diff --git a/pkg/dart2wasm/lib/js/util.dart b/pkg/dart2wasm/lib/js/util.dart
index 13590be258e..f643a28f4f8 100644
--- a/pkg/dart2wasm/lib/js/util.dart
+++ b/pkg/dart2wasm/lib/js/util.dart
@@ -129,44 +129,94 @@ class CoreTypesUtil {
     coreTypes.functionClass: jsifyFunction,
   };
 
-  late final Map<Class, Procedure> _dartifyMap = {
+  /// Conversion functions from `WasmExternRef?`. These functions should check
+  /// for `null` and `undefined` values, and types to prevent nulls from flowing
+  /// into non-nullable Dart values or wrapping references with incorrect types.
+  /// (e.g. a `String` as `Uint8list`)
+  ///
+  /// Return values should be non-nullable.
+  late final Map<Class, Procedure> _dartifyNonNullableMap = {
     coreTypes.boolClass:
         coreTypes.index.getTopLevelProcedure('dart:_js_helper', 'toDartBool'),
     coreTypes.intClass:
-        coreTypes.index.getTopLevelProcedure('dart:_js_helper', 'dartifyInt'),
+        coreTypes.index.getTopLevelProcedure('dart:_js_helper', 'toDartInt'),
     coreTypes.doubleClass:
-        coreTypes.index.getTopLevelProcedure('dart:_js_helper', 'toDartNumber'),
+        coreTypes.index.getTopLevelProcedure('dart:_js_helper', 'toDartDouble'),
     coreTypes.numClass:
-        coreTypes.index.getTopLevelProcedure('dart:_js_helper', 'toDartNumber'),
+        coreTypes.index.getTopLevelProcedure('dart:_js_helper', 'toDartDouble'),
     coreTypes.stringClass:
         coreTypes.index.getProcedure('dart:_string', 'JSStringImpl', 'fromRef'),
     coreTypes.listClass:
         coreTypes.index.getTopLevelProcedure('dart:_js_helper', 'toDartList'),
     coreTypes.index.getClass('dart:typed_data', 'Int8List'): coreTypes.index
-        .getProcedure('dart:_js_types', 'JSInt8ArrayImpl', 'fromArrayRef'),
+        .getProcedure('dart:_js_types', 'JSInt8ArrayImpl', 'fromRef'),
     coreTypes.index.getClass('dart:typed_data', 'Uint8List'): coreTypes.index
-        .getProcedure('dart:_js_types', 'JSUint8ArrayImpl', 'fromArrayRef'),
-    coreTypes.index.getClass('dart:typed_data', 'Uint8ClampedList'):
-        coreTypes.index.getProcedure(
-            'dart:_js_types', 'JSUint8ClampedArrayImpl', 'fromArrayRef'),
+        .getProcedure('dart:_js_types', 'JSUint8ArrayImpl', 'fromRef'),
+    coreTypes.index.getClass('dart:typed_data', 'Uint8ClampedList'): coreTypes
+        .index
+        .getProcedure('dart:_js_types', 'JSUint8ClampedArrayImpl', 'fromRef'),
     coreTypes.index.getClass('dart:typed_data', 'Int16List'): coreTypes.index
-        .getProcedure('dart:_js_types', 'JSInt16ArrayImpl', 'fromArrayRef'),
+        .getProcedure('dart:_js_types', 'JSInt16ArrayImpl', 'fromRef'),
     coreTypes.index.getClass('dart:typed_data', 'Uint16List'): coreTypes.index
-        .getProcedure('dart:_js_types', 'JSUint16ArrayImpl', 'fromArrayRef'),
+        .getProcedure('dart:_js_types', 'JSUint16ArrayImpl', 'fromRef'),
     coreTypes.index.getClass('dart:typed_data', 'Int32List'): coreTypes.index
-        .getProcedure('dart:_js_types', 'JSInt32ArrayImpl', 'fromArrayRef'),
+        .getProcedure('dart:_js_types', 'JSInt32ArrayImpl', 'fromRef'),
     coreTypes.index.getClass('dart:typed_data', 'Uint32List'): coreTypes.index
-        .getProcedure('dart:_js_types', 'JSUint32ArrayImpl', 'fromArrayRef'),
+        .getProcedure('dart:_js_types', 'JSUint32ArrayImpl', 'fromRef'),
     coreTypes.index.getClass('dart:typed_data', 'Float32List'): coreTypes.index
-        .getProcedure('dart:_js_types', 'JSFloat32ArrayImpl', 'fromArrayRef'),
+        .getProcedure('dart:_js_types', 'JSFloat32ArrayImpl', 'fromRef'),
     coreTypes.index.getClass('dart:typed_data', 'Float64List'): coreTypes.index
-        .getProcedure('dart:_js_types', 'JSFloat64ArrayImpl', 'fromArrayRef'),
+        .getProcedure('dart:_js_types', 'JSFloat64ArrayImpl', 'fromRef'),
     coreTypes.index.getClass('dart:typed_data', 'ByteBuffer'): coreTypes.index
         .getProcedure('dart:_js_types', 'JSArrayBufferImpl', 'fromRef'),
     coreTypes.index.getClass('dart:typed_data', 'ByteData'): coreTypes.index
         .getProcedure('dart:_js_types', 'JSDataViewImpl', 'fromRef'),
   };
 
+  /// Similar to [_dartifyNonNullableMap], but return values should be nullable.
+  ///
+  /// These shouldn't throw on `null` or `undefined` arguments and instead
+  /// return Dart `null`.
+  late final Map<Class, Procedure> _dartifyNullableMap = {
+    coreTypes.boolClass: coreTypes.index
+        .getTopLevelProcedure('dart:_js_helper', 'toDartNullableBool'),
+    coreTypes.intClass: coreTypes.index
+        .getTopLevelProcedure('dart:_js_helper', 'toDartNullableInt'),
+    coreTypes.doubleClass: coreTypes.index
+        .getTopLevelProcedure('dart:_js_helper', 'toDartNullableDouble'),
+    coreTypes.numClass: coreTypes.index
+        .getTopLevelProcedure('dart:_js_helper', 'toDartNullableDouble'),
+    coreTypes.stringClass: coreTypes.index
+        .getProcedure('dart:_string', 'JSStringImpl', 'fromRefNullable'),
+    coreTypes.listClass: coreTypes.index
+        .getTopLevelProcedure('dart:_js_helper', 'toDartNullableList'),
+    coreTypes.index.getClass('dart:typed_data', 'Int8List'): coreTypes.index
+        .getProcedure('dart:_js_types', 'JSInt8ArrayImpl', 'fromRefNullable'),
+    coreTypes.index.getClass('dart:typed_data', 'Uint8List'): coreTypes.index
+        .getProcedure('dart:_js_types', 'JSUint8ArrayImpl', 'fromRefNullable'),
+    coreTypes.index.getClass('dart:typed_data', 'Uint8ClampedList'):
+        coreTypes.index.getProcedure(
+            'dart:_js_types', 'JSUint8ClampedArrayImpl', 'fromRefNullable'),
+    coreTypes.index.getClass('dart:typed_data', 'Int16List'): coreTypes.index
+        .getProcedure('dart:_js_types', 'JSInt16ArrayImpl', 'fromRefNullable'),
+    coreTypes.index.getClass('dart:typed_data', 'Uint16List'): coreTypes.index
+        .getProcedure('dart:_js_types', 'JSUint16ArrayImpl', 'fromRefNullable'),
+    coreTypes.index.getClass('dart:typed_data', 'Int32List'): coreTypes.index
+        .getProcedure('dart:_js_types', 'JSInt32ArrayImpl', 'fromRefNullable'),
+    coreTypes.index.getClass('dart:typed_data', 'Uint32List'): coreTypes.index
+        .getProcedure('dart:_js_types', 'JSUint32ArrayImpl', 'fromRefNullable'),
+    coreTypes.index.getClass('dart:typed_data', 'Float32List'): coreTypes.index
+        .getProcedure(
+            'dart:_js_types', 'JSFloat32ArrayImpl', 'fromRefNullable'),
+    coreTypes.index.getClass('dart:typed_data', 'Float64List'): coreTypes.index
+        .getProcedure(
+            'dart:_js_types', 'JSFloat64ArrayImpl', 'fromRefNullable'),
+    coreTypes.index.getClass('dart:typed_data', 'ByteBuffer'): coreTypes.index
+        .getProcedure('dart:_js_types', 'JSArrayBufferImpl', 'fromRefNullable'),
+    coreTypes.index.getClass('dart:typed_data', 'ByteData'): coreTypes.index
+        .getProcedure('dart:_js_types', 'JSDataViewImpl', 'fromRefNullable'),
+  };
+
   CoreTypesUtil(this.coreTypes, this.extensionIndex)
       : dartifyRawTarget = coreTypes.index
             .getTopLevelProcedure('dart:_js_helper', 'dartifyRaw'),
@@ -367,6 +417,9 @@ class CoreTypesUtil {
       );
 
   /// Cast the [invocation] if needed to conform to the expected [expectedType].
+  ///
+  /// [expectedType] is the return type of the interop function, as written by
+  /// the user.
   Expression castInvocationForReturn(
       Expression invocation, DartType expectedType) {
     Expression expression;
@@ -381,9 +434,6 @@ class CoreTypesUtil {
     }
 
     if (isJSValueType(expectedType)) {
-      // TODO(joshualitt): Expose boxed `JSNull` and `JSUndefined` to Dart
-      // code after migrating existing users of js interop on Dart2Wasm.
-      // expression = _createJSValue(invocation);
       // Casts are expensive, so we stick to a null-assertion if needed. If
       // the nullability can't be determined, cast.
       expression = invokeOneArg(jsValueBoxTarget, invocation);
@@ -396,27 +446,16 @@ class CoreTypesUtil {
     } else {
       final expectedTypeExtensionTypeErasure =
           expectedType.extensionTypeErasure;
-      final expectNullable =
-          expectedTypeExtensionTypeErasure.isPotentiallyNullable;
       final conversionProcedure =
           _dartConversionProcedure(expectedTypeExtensionTypeErasure);
       final invocationValueVar = VariableDeclaration('#jsInvocation',
           initializer: invocation,
           type: nullableWasmExternRefType,
           isSynthesized: true);
-      expression = Let(
-        invocationValueVar,
-        ConditionalExpression(
-          StaticInvocation(
-              isDartNullTarget, Arguments([VariableGet(invocationValueVar)])),
-          expectNullable
-              ? NullLiteral()
-              : StaticInvocation(throwArgumentNullErrorTarget, Arguments([])),
-          invokeOneArg(conversionProcedure, VariableGet(invocationValueVar)),
-          expectedType,
-        ),
-      );
+      expression = Let(invocationValueVar,
+          invokeOneArg(conversionProcedure, VariableGet(invocationValueVar)));
     }
+
     return expression;
   }
 
@@ -505,12 +544,13 @@ class CoreTypesUtil {
   /// type.
   ///
   /// The value passed to the returned conversion function should be an
-  /// `externref` and should be tested for `null` and `undefined`. The returned
-  /// procedures do not handle `null`s and `undefined`s.
+  /// `externref`.
   Procedure _dartConversionProcedure(DartType expectedType) {
     Procedure? conversionProcedure;
     if (expectedType is InterfaceType) {
-      conversionProcedure = _dartifyMap[expectedType.classNode];
+      conversionProcedure = expectedType.isPotentiallyNullable
+          ? _dartifyNullableMap[expectedType.classNode]
+          : _dartifyNonNullableMap[expectedType.classNode];
     }
     return conversionProcedure ?? dartifyRawTarget;
   }
diff --git a/pkg/dart2wasm/test/ir_tests/dyn_closure.wat b/pkg/dart2wasm/test/ir_tests/dyn_closure.wat
index 0b339c03dd6..ee9aee94eb3 100644
--- a/pkg/dart2wasm/test/ir_tests/dyn_closure.wat
+++ b/pkg/dart2wasm/test/ir_tests/dyn_closure.wat
@@ -27,7 +27,7 @@
     (i32.const 0)
     (global.get $global0)
     (ref.func $"foo tear-off trampoline")
-    (ref.func $"foo tear-off trampoline_316")
+    (ref.func $"foo tear-off trampoline_319")
     (struct.new $#Vtable-0-2)
     (i32.const 12)
     (i32.const 0)
@@ -52,7 +52,7 @@
     (i32.const 0)
     (global.get $global0)
     (ref.func $"bar tear-off trampoline")
-    (ref.func $"bar tear-off trampoline_319")
+    (ref.func $"bar tear-off trampoline_322")
     (struct.new $#Vtable-0-2)
     (i32.const 12)
     (i32.const 0)
@@ -74,7 +74,7 @@
     (struct.new $#Closure-0-2))
   (global $global0 (ref $#DummyStruct) <...>)
   (func $bar tear-off trampoline (param $var0 (ref struct)) (param $var1 (ref null $#Top)) (result (ref null $#Top)) <...>)
-  (func $bar tear-off trampoline_319 (param $var0 (ref struct)) (param $var1 (ref null $#Top)) (param $var2 (ref null $#Top)) (result (ref null $#Top)) <...>)
+  (func $bar tear-off trampoline_322 (param $var0 (ref struct)) (param $var1 (ref null $#Top)) (param $var2 (ref null $#Top)) (result (ref null $#Top)) <...>)
   (func $foo tear-off trampoline (param $var0 (ref struct)) (param $var1 (ref null $#Top)) (result (ref null $#Top)) <...>)
-  (func $foo tear-off trampoline_316 (param $var0 (ref struct)) (param $var1 (ref null $#Top)) (param $var2 (ref null $#Top)) (result (ref null $#Top)) <...>)
+  (func $foo tear-off trampoline_319 (param $var0 (ref struct)) (param $var1 (ref null $#Top)) (param $var2 (ref null $#Top)) (result (ref null $#Top)) <...>)
 )
\ No newline at end of file
diff --git a/pkg/dart2wasm/test/ir_tests/dyn_closure_function_apply.wat b/pkg/dart2wasm/test/ir_tests/dyn_closure_function_apply.wat
index 6592f029c26..f37255502e8 100644
--- a/pkg/dart2wasm/test/ir_tests/dyn_closure_function_apply.wat
+++ b/pkg/dart2wasm/test/ir_tests/dyn_closure_function_apply.wat
@@ -27,7 +27,7 @@
     (i32.const 0)
     (global.get $global0)
     (ref.func $"foo tear-off trampoline")
-    (ref.func $"foo tear-off trampoline_316")
+    (ref.func $"foo tear-off trampoline_319")
     (struct.new $#Vtable-0-2)
     (i32.const 12)
     (i32.const 0)
@@ -52,7 +52,7 @@
     (i32.const 0)
     (global.get $global0)
     (ref.func $"bar tear-off trampoline")
-    (ref.func $"bar tear-off trampoline_321")
+    (ref.func $"bar tear-off trampoline_324")
     (struct.new $#Vtable-0-2)
     (i32.const 12)
     (i32.const 0)
@@ -74,7 +74,7 @@
     (struct.new $#Closure-0-2))
   (global $global0 (ref $#DummyStruct) <...>)
   (func $bar tear-off trampoline (param $var0 (ref struct)) (param $var1 (ref null $#Top)) (result (ref null $#Top)) <...>)
-  (func $bar tear-off trampoline_321 (param $var0 (ref struct)) (param $var1 (ref null $#Top)) (param $var2 (ref null $#Top)) (result (ref null $#Top)) <...>)
+  (func $bar tear-off trampoline_324 (param $var0 (ref struct)) (param $var1 (ref null $#Top)) (param $var2 (ref null $#Top)) (result (ref null $#Top)) <...>)
   (func $foo tear-off trampoline (param $var0 (ref struct)) (param $var1 (ref null $#Top)) (result (ref null $#Top)) <...>)
-  (func $foo tear-off trampoline_316 (param $var0 (ref struct)) (param $var1 (ref null $#Top)) (param $var2 (ref null $#Top)) (result (ref null $#Top)) <...>)
+  (func $foo tear-off trampoline_319 (param $var0 (ref struct)) (param $var1 (ref null $#Top)) (param $var2 (ref null $#Top)) (result (ref null $#Top)) <...>)
 )
\ No newline at end of file
diff --git a/pkg/dart2wasm/test/ir_tests/dyn_closure_function_apply_named.wat b/pkg/dart2wasm/test/ir_tests/dyn_closure_function_apply_named.wat
index 2123b909597..2d5601d420a 100644
--- a/pkg/dart2wasm/test/ir_tests/dyn_closure_function_apply_named.wat
+++ b/pkg/dart2wasm/test/ir_tests/dyn_closure_function_apply_named.wat
@@ -31,7 +31,7 @@
     (i32.const 0)
     (global.get $global0)
     (ref.func $"foo tear-off dynamic call entry")
-    (ref.func $"foo tear-off trampoline_324")
+    (ref.func $"foo tear-off trampoline_327")
     (struct.new $#Vtable-0-2)
     (i32.const 12)
     (i32.const 0)
@@ -57,7 +57,7 @@
     (i32.const 0)
     (global.get $global0)
     (ref.func $"bar tear-off dynamic call entry")
-    (ref.func $"bar tear-off trampoline_330")
+    (ref.func $"bar tear-off trampoline_333")
     (struct.new $#Vtable-0-2)
     (i32.const 12)
     (i32.const 0)
@@ -74,7 +74,7 @@
     (struct.new $#Closure-0-2))
   (global $global0 (ref $#DummyStruct) <...>)
   (func $bar tear-off dynamic call entry (param $var0 (ref $#Closure-0-0)) (param $var1 (ref $Array<_Type>)) (param $var2 (ref $Array<Object?>)) (param $var3 (ref $Array<Object?>)) (result (ref null $#Top)) <...>)
-  (func $bar tear-off trampoline_330 (param $var0 (ref struct)) (param $var1 (ref null $#Top)) (param $var2 (ref null $#Top)) (result (ref null $#Top)) <...>)
+  (func $bar tear-off trampoline_333 (param $var0 (ref struct)) (param $var1 (ref null $#Top)) (param $var2 (ref null $#Top)) (result (ref null $#Top)) <...>)
   (func $foo tear-off dynamic call entry (param $var0 (ref $#Closure-0-0)) (param $var1 (ref $Array<_Type>)) (param $var2 (ref $Array<Object?>)) (param $var3 (ref $Array<Object?>)) (result (ref null $#Top)) <...>)
-  (func $foo tear-off trampoline_324 (param $var0 (ref struct)) (param $var1 (ref null $#Top)) (param $var2 (ref null $#Top)) (result (ref null $#Top)) <...>)
+  (func $foo tear-off trampoline_327 (param $var0 (ref struct)) (param $var1 (ref null $#Top)) (param $var2 (ref null $#Top)) (result (ref null $#Top)) <...>)
 )
\ No newline at end of file
diff --git a/pkg/dart2wasm/test/ir_tests/interop.bool.wat b/pkg/dart2wasm/test/ir_tests/interop.bool.wat
index 7a60cc298f0..ceb68af3f4c 100644
--- a/pkg/dart2wasm/test/ir_tests/interop.bool.wat
+++ b/pkg/dart2wasm/test/ir_tests/interop.bool.wat
@@ -1,71 +1,39 @@
 (module $module0
   (type $#Top (struct
     (field $field0 i32)))
-  (func $"dart2wasm._170 (import)" (import "dart2wasm" "_170") (param externref) (result i32))
-  (func $"dart2wasm._171 (import)" (import "dart2wasm" "_171") (param i32) (result externref))
-  (func $"dart2wasm._295 (import)" (import "dart2wasm" "_295") (param externref) (result externref))
-  (func $"dart2wasm._296 (import)" (import "dart2wasm" "_296") (param externref) (result externref))
+  (func $"dart2wasm._174 (import)" (import "dart2wasm" "_174") (param i32) (result externref))
+  (func $"dart2wasm._298 (import)" (import "dart2wasm" "_298") (param externref) (result externref))
+  (func $"dart2wasm._299 (import)" (import "dart2wasm" "_299") (param externref) (result externref))
   (global $"C2 false" (ref $#Top) <...>)
   (global $"C40 true" (ref $#Top) <...>)
   (global $"boolValueNullable initialized" (mut i32) <...>)
   (global $boolValueNullable (mut (ref null $#Top)) <...>)
-  (func $_throwArgumentNullError <noInline>  <...>)
   (func $boolValue implicit getter (result i32) <...>)
   (func $ktrue implicit getter (result i32) <...>)
   (func $sinkBool <noInline> (param $var0 i32) <...>)
   (func $sinkBoolNullable <noInline> (param $var0 (ref null $#Top)) <...>)
   (func $"testBoolConstant <noInline>"
-    (local $var0 externref)
     i32.const 1
-    call $"dart2wasm._171 (import)"
-    call $"dart2wasm._295 (import)"
-    local.tee $var0
-    call $isDartNull
-    if (result i32)
-      call $"_throwArgumentNullError <noInline>"
-      unreachable
-    else
-      local.get $var0
-      call $"dart2wasm._170 (import)"
-    end
+    call $"dart2wasm._174 (import)"
+    call $"dart2wasm._298 (import)"
+    call $toDartBool
     call $"sinkBool <noInline>"
   )
   (func $"testBoolConstantNullable <noInline>"
-    (local $var0 externref)
     ref.null noextern
-    call $"dart2wasm._296 (import)"
-    local.tee $var0
-    call $isDartNull
-    if (result (ref null $#Top))
-      ref.null none
-    else
-      global.get $"C40 true"
-      global.get $"C2 false"
-      local.get $var0
-      call $"dart2wasm._170 (import)"
-      select (ref $#Top)
-    end
+    call $"dart2wasm._299 (import)"
+    call $toDartNullableBool
     call $"sinkBoolNullable <noInline>"
   )
   (func $"testBoolValue <noInline>"
-    (local $var0 externref)
     call $"boolValue implicit getter"
-    call $"dart2wasm._171 (import)"
-    call $"dart2wasm._295 (import)"
-    local.tee $var0
-    call $isDartNull
-    if (result i32)
-      call $"_throwArgumentNullError <noInline>"
-      unreachable
-    else
-      local.get $var0
-      call $"dart2wasm._170 (import)"
-    end
+    call $"dart2wasm._174 (import)"
+    call $"dart2wasm._298 (import)"
+    call $toDartBool
     call $"sinkBool <noInline>"
   )
   (func $"testBoolValueNullable <noInline>"
     (local $var0 (ref null $#Top))
-    (local $var1 externref)
     global.get $"boolValueNullable initialized"
     i32.eqz
     if
@@ -91,20 +59,11 @@
       local.get $var0
       call $jsifyRaw
     end
-    call $"dart2wasm._296 (import)"
-    local.tee $var1
-    call $isDartNull
-    if (result (ref null $#Top))
-      ref.null none
-    else
-      global.get $"C40 true"
-      global.get $"C2 false"
-      local.get $var1
-      call $"dart2wasm._170 (import)"
-      select (ref $#Top)
-    end
+    call $"dart2wasm._299 (import)"
+    call $toDartNullableBool
     call $"sinkBoolNullable <noInline>"
   )
-  (func $isDartNull (param $var0 externref) (result i32) <...>)
   (func $jsifyRaw (param $var0 (ref null $#Top)) (result externref) <...>)
+  (func $toDartBool (param $var0 externref) (result i32) <...>)
+  (func $toDartNullableBool (param $var0 externref) (result (ref null $#Top)) <...>)
 )
\ No newline at end of file
diff --git a/pkg/dart2wasm/test/ir_tests/interop.double.wat b/pkg/dart2wasm/test/ir_tests/interop.double.wat
index 4a35b25ff79..b9039284752 100644
--- a/pkg/dart2wasm/test/ir_tests/interop.double.wat
+++ b/pkg/dart2wasm/test/ir_tests/interop.double.wat
@@ -4,65 +4,34 @@
   (type $BoxedDouble (sub final $#Top (struct
     (field $field0 i32)
     (field $value f64))))
-  (func $"dart2wasm._168 (import)" (import "dart2wasm" "_168") (param externref) (result f64))
-  (func $"dart2wasm._295 (import)" (import "dart2wasm" "_295") (param f64) (result externref))
-  (func $"dart2wasm._296 (import)" (import "dart2wasm" "_296") (param externref) (result externref))
+  (func $"dart2wasm._298 (import)" (import "dart2wasm" "_298") (param f64) (result externref))
+  (func $"dart2wasm._299 (import)" (import "dart2wasm" "_299") (param externref) (result externref))
   (global $"doubleValueNullable initialized" (mut i32) <...>)
   (global $doubleValueNullable (mut (ref null $BoxedDouble)) <...>)
-  (func $_throwArgumentNullError <noInline>  <...>)
   (func $doubleValue implicit getter (result f64) <...>)
   (func $ktrue implicit getter (result i32) <...>)
   (func $sinkDouble <noInline> (param $var0 f64) <...>)
   (func $sinkDoubleNullable <noInline> (param $var0 (ref null $BoxedDouble)) <...>)
   (func $"testDoubleConstant <noInline>"
-    (local $var0 externref)
     f64.const 1.1
-    call $"dart2wasm._295 (import)"
-    local.tee $var0
-    call $isDartNull
-    if (result f64)
-      call $"_throwArgumentNullError <noInline>"
-      unreachable
-    else
-      local.get $var0
-      call $"dart2wasm._168 (import)"
-    end
+    call $"dart2wasm._298 (import)"
+    call $toDartDouble
     call $"sinkDouble <noInline>"
   )
   (func $"testDoubleConstantNullable <noInline>"
-    (local $var0 externref)
     ref.null noextern
-    call $"dart2wasm._296 (import)"
-    local.tee $var0
-    call $isDartNull
-    if (result (ref null $BoxedDouble))
-      ref.null none
-    else
-      i32.const 87
-      local.get $var0
-      call $"dart2wasm._168 (import)"
-      struct.new $BoxedDouble
-    end
+    call $"dart2wasm._299 (import)"
+    call $toDartNullableDouble
     call $"sinkDoubleNullable <noInline>"
   )
   (func $"testDoubleValue <noInline>"
-    (local $var0 externref)
     call $"doubleValue implicit getter"
-    call $"dart2wasm._295 (import)"
-    local.tee $var0
-    call $isDartNull
-    if (result f64)
-      call $"_throwArgumentNullError <noInline>"
-      unreachable
-    else
-      local.get $var0
-      call $"dart2wasm._168 (import)"
-    end
+    call $"dart2wasm._298 (import)"
+    call $toDartDouble
     call $"sinkDouble <noInline>"
   )
   (func $"testDoubleValueNullable <noInline>"
     (local $var0 (ref null $BoxedDouble))
-    (local $var1 externref)
     global.get $"doubleValueNullable initialized"
     i32.eqz
     if
@@ -87,19 +56,11 @@
       local.get $var0
       call $jsifyRaw
     end
-    call $"dart2wasm._296 (import)"
-    local.tee $var1
-    call $isDartNull
-    if (result (ref null $BoxedDouble))
-      ref.null none
-    else
-      i32.const 87
-      local.get $var1
-      call $"dart2wasm._168 (import)"
-      struct.new $BoxedDouble
-    end
+    call $"dart2wasm._299 (import)"
+    call $toDartNullableDouble
     call $"sinkDoubleNullable <noInline>"
   )
-  (func $isDartNull (param $var0 externref) (result i32) <...>)
   (func $jsifyRaw (param $var0 (ref null $#Top)) (result externref) <...>)
+  (func $toDartDouble (param $var0 externref) (result f64) <...>)
+  (func $toDartNullableDouble (param $var0 externref) (result (ref null $BoxedDouble)) <...>)
 )
\ No newline at end of file
diff --git a/pkg/dart2wasm/test/ir_tests/interop.int.wat b/pkg/dart2wasm/test/ir_tests/interop.int.wat
index d00b5b435f1..b262fddda41 100644
--- a/pkg/dart2wasm/test/ir_tests/interop.int.wat
+++ b/pkg/dart2wasm/test/ir_tests/interop.int.wat
@@ -4,66 +4,36 @@
   (type $BoxedInt (sub $#Top (struct
     (field $field0 i32)
     (field $value i64))))
-  (func $"dart2wasm._295 (import)" (import "dart2wasm" "_295") (param externref) (result externref))
-  (func $"dart2wasm._296 (import)" (import "dart2wasm" "_296") (param externref) (result externref))
+  (func $"dart2wasm._298 (import)" (import "dart2wasm" "_298") (param externref) (result externref))
+  (func $"dart2wasm._299 (import)" (import "dart2wasm" "_299") (param externref) (result externref))
   (global $"intValueNullable initialized" (mut i32) <...>)
   (global $intValueNullable (mut (ref null $BoxedInt)) <...>)
-  (func $_throwArgumentNullError <noInline>  <...>)
   (func $intValue implicit getter (result i64) <...>)
   (func $ktrue implicit getter (result i32) <...>)
   (func $sinkInt <noInline> (param $var0 i64) <...>)
   (func $sinkIntNullable <noInline> (param $var0 (ref null $BoxedInt)) <...>)
   (func $"testIntConstant <noInline>"
-    (local $var0 externref)
     i64.const 1
     call $jsifyInt
-    call $"dart2wasm._295 (import)"
-    local.tee $var0
-    call $isDartNull
-    if (result i64)
-      call $"_throwArgumentNullError <noInline>"
-      unreachable
-    else
-      local.get $var0
-      call $dartifyInt
-    end
+    call $"dart2wasm._298 (import)"
+    call $toDartInt
     call $"sinkInt <noInline>"
   )
   (func $"testIntConstantNullable <noInline>"
-    (local $var0 externref)
     ref.null noextern
-    call $"dart2wasm._296 (import)"
-    local.tee $var0
-    call $isDartNull
-    if (result (ref null $BoxedInt))
-      ref.null none
-    else
-      i32.const 69
-      local.get $var0
-      call $dartifyInt
-      struct.new $BoxedInt
-    end
+    call $"dart2wasm._299 (import)"
+    call $toDartNullableInt
     call $"sinkIntNullable <noInline>"
   )
   (func $"testIntValue <noInline>"
-    (local $var0 externref)
     call $"intValue implicit getter"
     call $jsifyInt
-    call $"dart2wasm._295 (import)"
-    local.tee $var0
-    call $isDartNull
-    if (result i64)
-      call $"_throwArgumentNullError <noInline>"
-      unreachable
-    else
-      local.get $var0
-      call $dartifyInt
-    end
+    call $"dart2wasm._298 (import)"
+    call $toDartInt
     call $"sinkInt <noInline>"
   )
   (func $"testIntValueNullable <noInline>"
     (local $var0 (ref null $BoxedInt))
-    (local $var1 externref)
     global.get $"intValueNullable initialized"
     i32.eqz
     if
@@ -88,21 +58,12 @@
       local.get $var0
       call $jsifyRaw
     end
-    call $"dart2wasm._296 (import)"
-    local.tee $var1
-    call $isDartNull
-    if (result (ref null $BoxedInt))
-      ref.null none
-    else
-      i32.const 69
-      local.get $var1
-      call $dartifyInt
-      struct.new $BoxedInt
-    end
+    call $"dart2wasm._299 (import)"
+    call $toDartNullableInt
     call $"sinkIntNullable <noInline>"
   )
-  (func $dartifyInt (param $var0 externref) (result i64) <...>)
-  (func $isDartNull (param $var0 externref) (result i32) <...>)
   (func $jsifyInt (param $var0 i64) (result externref) <...>)
   (func $jsifyRaw (param $var0 (ref null $#Top)) (result externref) <...>)
+  (func $toDartInt (param $var0 externref) (result i64) <...>)
+  (func $toDartNullableInt (param $var0 externref) (result (ref null $BoxedInt)) <...>)
 )
\ No newline at end of file
diff --git a/pkg/dart2wasm/test/ir_tests/interop.num.wat b/pkg/dart2wasm/test/ir_tests/interop.num.wat
index 9b41ff7d4b1..d6b712e6964 100644
--- a/pkg/dart2wasm/test/ir_tests/interop.num.wat
+++ b/pkg/dart2wasm/test/ir_tests/interop.num.wat
@@ -4,84 +4,44 @@
   (type $BoxedDouble (sub final $#Top (struct
     (field $field0 i32)
     (field $value f64))))
-  (func $"dart2wasm._168 (import)" (import "dart2wasm" "_168") (param externref) (result f64))
-  (func $"dart2wasm._169 (import)" (import "dart2wasm" "_169") (param f64) (result externref))
-  (func $"dart2wasm._295 (import)" (import "dart2wasm" "_295") (param externref) (result externref))
-  (func $"dart2wasm._296 (import)" (import "dart2wasm" "_296") (param externref) (result externref))
+  (func $"dart2wasm._171 (import)" (import "dart2wasm" "_171") (param f64) (result externref))
+  (func $"dart2wasm._298 (import)" (import "dart2wasm" "_298") (param externref) (result externref))
+  (func $"dart2wasm._299 (import)" (import "dart2wasm" "_299") (param externref) (result externref))
   (global $"numValueNullable initialized" (mut i32) <...>)
   (global $numValueNullable (mut (ref null $#Top)) <...>)
-  (func $_throwArgumentNullError <noInline>  <...>)
   (func $ktrue implicit getter (result i32) <...>)
   (func $numValue implicit getter (result (ref $#Top)) <...>)
   (func $sinkNum <noInline> (param $var0 f64) <...>)
   (func $sinkNumNullable <noInline> (param $var0 (ref null $BoxedDouble)) <...>)
   (func $"testNumConstant <noInline>"
-    (local $var0 externref)
     i64.const 1
     call $jsifyInt
-    call $"dart2wasm._295 (import)"
-    local.tee $var0
-    call $isDartNull
-    if (result f64)
-      call $"_throwArgumentNullError <noInline>"
-      unreachable
-    else
-      local.get $var0
-      call $"dart2wasm._168 (import)"
-    end
+    call $"dart2wasm._298 (import)"
+    call $toDartDouble
     call $"sinkNum <noInline>"
   )
   (func $"testNumConstantDouble <noInline>"
-    (local $var0 externref)
     f64.const 1.1
-    call $"dart2wasm._169 (import)"
-    call $"dart2wasm._295 (import)"
-    local.tee $var0
-    call $isDartNull
-    if (result f64)
-      call $"_throwArgumentNullError <noInline>"
-      unreachable
-    else
-      local.get $var0
-      call $"dart2wasm._168 (import)"
-    end
+    call $"dart2wasm._171 (import)"
+    call $"dart2wasm._298 (import)"
+    call $toDartDouble
     call $"sinkNum <noInline>"
   )
   (func $"testNumConstantNullable <noInline>"
-    (local $var0 externref)
     ref.null noextern
-    call $"dart2wasm._296 (import)"
-    local.tee $var0
-    call $isDartNull
-    if (result (ref null $BoxedDouble))
-      ref.null none
-    else
-      i32.const 87
-      local.get $var0
-      call $"dart2wasm._168 (import)"
-      struct.new $BoxedDouble
-    end
+    call $"dart2wasm._299 (import)"
+    call $toDartNullableDouble
     call $"sinkNumNullable <noInline>"
   )
   (func $"testNumValue <noInline>"
-    (local $var0 externref)
     call $"numValue implicit getter"
     call $jsifyNum
-    call $"dart2wasm._295 (import)"
-    local.tee $var0
-    call $isDartNull
-    if (result f64)
-      call $"_throwArgumentNullError <noInline>"
-      unreachable
-    else
-      local.get $var0
-      call $"dart2wasm._168 (import)"
-    end
+    call $"dart2wasm._298 (import)"
+    call $toDartDouble
     call $"sinkNum <noInline>"
   )
   (func $"testNumValueNullable <noInline>"
     (local $var0 (ref null $#Top))
-    (local $var1 externref)
     global.get $"numValueNullable initialized"
     i32.eqz
     if
@@ -104,21 +64,13 @@
       local.get $var0
       call $jsifyRaw
     end
-    call $"dart2wasm._296 (import)"
-    local.tee $var1
-    call $isDartNull
-    if (result (ref null $BoxedDouble))
-      ref.null none
-    else
-      i32.const 87
-      local.get $var1
-      call $"dart2wasm._168 (import)"
-      struct.new $BoxedDouble
-    end
+    call $"dart2wasm._299 (import)"
+    call $toDartNullableDouble
     call $"sinkNumNullable <noInline>"
   )
-  (func $isDartNull (param $var0 externref) (result i32) <...>)
   (func $jsifyInt (param $var0 i64) (result externref) <...>)
   (func $jsifyNum (param $var0 (ref $#Top)) (result externref) <...>)
   (func $jsifyRaw (param $var0 (ref null $#Top)) (result externref) <...>)
+  (func $toDartDouble (param $var0 externref) (result f64) <...>)
+  (func $toDartNullableDouble (param $var0 externref) (result (ref null $BoxedDouble)) <...>)
 )
\ No newline at end of file
diff --git a/pkg/dart2wasm/test/ir_tests/interop.string.wat b/pkg/dart2wasm/test/ir_tests/interop.string.wat
index a5171ac7abf..937c0257823 100644
--- a/pkg/dart2wasm/test/ir_tests/interop.string.wat
+++ b/pkg/dart2wasm/test/ir_tests/interop.string.wat
@@ -4,65 +4,37 @@
   (type $JSStringImpl (sub final $#Top (struct
     (field $field0 i32)
     (field $_ref externref))))
-  (func $"dart2wasm._295 (import)" (import "dart2wasm" "_295") (param externref) (result externref))
-  (func $"dart2wasm._296 (import)" (import "dart2wasm" "_296") (param externref) (result externref))
+  (func $"dart2wasm._298 (import)" (import "dart2wasm" "_298") (param externref) (result externref))
+  (func $"dart2wasm._299 (import)" (import "dart2wasm" "_299") (param externref) (result externref))
   (global $.a (import "" "a") (ref extern))
   (global $"stringValueNullable initialized" (mut i32) <...>)
   (global $stringValueNullable (mut (ref null $JSStringImpl)) <...>)
-  (func $_throwArgumentNullError <noInline>  <...>)
   (func $ktrue implicit getter (result i32) <...>)
   (func $new JSStringImpl.fromRef (param $var0 externref) (result (ref $JSStringImpl)) <...>)
   (func $sinkString <noInline> (param $var0 (ref $JSStringImpl)) <...>)
   (func $sinkStringNullable <noInline> (param $var0 (ref null $JSStringImpl)) <...>)
   (func $stringValue implicit getter (result (ref $JSStringImpl)) <...>)
   (func $"testStringConstant <noInline>"
-    (local $var0 externref)
     global.get $.a
-    call $"dart2wasm._295 (import)"
-    local.tee $var0
-    call $isDartNull
-    if (result (ref $JSStringImpl))
-      call $"_throwArgumentNullError <noInline>"
-      unreachable
-    else
-      local.get $var0
-      call $"new JSStringImpl.fromRef"
-    end
+    call $"dart2wasm._298 (import)"
+    call $"new JSStringImpl.fromRef"
     call $"sinkString <noInline>"
   )
   (func $"testStringConstantNullable <noInline>"
-    (local $var0 externref)
     ref.null noextern
-    call $"dart2wasm._296 (import)"
-    local.tee $var0
-    call $isDartNull
-    if (result (ref null $JSStringImpl))
-      ref.null none
-    else
-      local.get $var0
-      call $"new JSStringImpl.fromRef"
-    end
+    call $"dart2wasm._299 (import)"
+    call $JSStringImpl.fromRefNullable
     call $"sinkStringNullable <noInline>"
   )
   (func $"testStringValue <noInline>"
-    (local $var0 externref)
     call $"stringValue implicit getter"
     struct.get $JSStringImpl $_ref
-    call $"dart2wasm._295 (import)"
-    local.tee $var0
-    call $isDartNull
-    if (result (ref $JSStringImpl))
-      call $"_throwArgumentNullError <noInline>"
-      unreachable
-    else
-      local.get $var0
-      call $"new JSStringImpl.fromRef"
-    end
+    call $"dart2wasm._298 (import)"
+    call $"new JSStringImpl.fromRef"
     call $"sinkString <noInline>"
   )
   (func $"testStringValueNullable <noInline>"
     (local $var0 (ref null $JSStringImpl))
-    (local $var1 externref)
     global.get $"stringValueNullable initialized"
     i32.eqz
     if
@@ -85,17 +57,10 @@
       local.get $var0
       call $jsifyRaw
     end
-    call $"dart2wasm._296 (import)"
-    local.tee $var1
-    call $isDartNull
-    if (result (ref null $JSStringImpl))
-      ref.null none
-    else
-      local.get $var1
-      call $"new JSStringImpl.fromRef"
-    end
+    call $"dart2wasm._299 (import)"
+    call $JSStringImpl.fromRefNullable
     call $"sinkStringNullable <noInline>"
   )
-  (func $isDartNull (param $var0 externref) (result i32) <...>)
+  (func $JSStringImpl.fromRefNullable (param $var0 externref) (result (ref null $JSStringImpl)) <...>)
   (func $jsifyRaw (param $var0 (ref null $#Top)) (result externref) <...>)
 )
\ No newline at end of file
diff --git a/sdk/lib/_internal/wasm/lib/js_helper.dart b/sdk/lib/_internal/wasm/lib/js_helper.dart
index 454566aec5d..e33ec5209a2 100644
--- a/sdk/lib/_internal/wasm/lib/js_helper.dart
+++ b/sdk/lib/_internal/wasm/lib/js_helper.dart
@@ -158,16 +158,88 @@ bool isJSRegExp(WasmExternRef? o) => JS<bool>("o => o instanceof RegExp", o);
 bool areEqualInJS(WasmExternRef? l, WasmExternRef? r) =>
     JS<bool>("(l, r) => l === r", l, r);
 
-// The JS runtime will run helpful conversion routines between refs and bool /
-// double. In the longer term hopefully we can find a way to avoid the round
-// trip.
-double toDartNumber(WasmExternRef? o) => JS<double>("o => o", o);
+@pragma('wasm:entry-point')
+double toDartDouble(WasmExternRef? ref) {
+  final numberType = _checkNumberType(ref);
+  if (numberType != 1) {
+    throw ArgumentError('JS value is not a number');
+  }
+  return _toDartDoubleUnchecked(ref);
+}
 
 @pragma('wasm:entry-point')
-WasmExternRef? toJSNumber(double o) => JS<WasmExternRef?>("o => o", o);
+double? toDartNullableDouble(WasmExternRef? ref) {
+  final refType = _checkNumberType(ref);
+  if (refType == 0) return null;
+  if (refType == 1) return _toDartDoubleUnchecked(ref);
+  throw ArgumentError('JS value is not a number');
+}
+
+double _toDartDoubleUnchecked(WasmExternRef? ref) => JS<double>("o => o", ref);
+
+int _checkNumberType(WasmExternRef? ref) {
+  return JS<WasmI32>("""o => {
+      if (o === undefined || o === null) return 0;
+      if (typeof o === 'number') return 1;
+      return 2;
+    }""", ref).toIntUnsigned();
+}
+
+int _jsNonNullToInt(WasmExternRef? ref, bool typeIsRight) {
+  if (typeIsRight) {
+    final dartDouble = _toDartDoubleUnchecked(ref);
+    if (dartDouble.isFinite) {
+      final dartInt = dartDouble.toInt();
+      if (dartInt.toDouble() == dartDouble) {
+        return dartInt;
+      }
+    }
+  }
+  throw ArgumentError('JS value is not integer');
+}
 
 @pragma('wasm:entry-point')
-bool toDartBool(WasmExternRef? o) => JS<bool>("o => o", o);
+int toDartInt(WasmExternRef? ref) {
+  final numberType = _checkNumberType(ref);
+  return _jsNonNullToInt(ref, numberType == 1);
+}
+
+@pragma('wasm:entry-point')
+int? toDartNullableInt(WasmExternRef? ref) {
+  final numberType = _checkNumberType(ref);
+  if (numberType == 0) return null;
+  return _jsNonNullToInt(ref, numberType == 1);
+}
+
+@pragma('wasm:entry-point')
+WasmExternRef? toJSNumber(double ref) => JS<WasmExternRef?>("o => o", ref);
+
+int _checkBoolType(WasmExternRef? ref) {
+  return JS<WasmI32>("""o => {
+      if (o === undefined || o === null) return 0;
+      if (typeof o === 'boolean') return 1;
+      return 2;
+    }""", ref).toIntUnsigned();
+}
+
+@pragma('wasm:entry-point')
+bool toDartBool(WasmExternRef? ref) {
+  final refType = _checkBoolType(ref);
+  if (refType != 1) {
+    throw ArgumentError('JS value is not a boolean');
+  }
+  return _toDartBoolUnchecked(ref);
+}
+
+@pragma('wasm:entry-point')
+bool? toDartNullableBool(WasmExternRef? ref) {
+  final refType = _checkBoolType(ref);
+  if (refType == 0) return null;
+  if (refType == 1) return _toDartBoolUnchecked(ref);
+  throw ArgumentError('JS value is not a boolean');
+}
+
+bool _toDartBoolUnchecked(WasmExternRef? ref) => JS<bool>("o => o", ref);
 
 WasmExternRef? toJSBoolean(bool b) => JS<WasmExternRef?>("b => !!b", b);
 
@@ -537,32 +609,28 @@ Object? dartifyRaw(WasmExternRef? ref, [int? refType]) {
   refType ??= externRefType(ref);
   return switch (refType) {
     ExternRefType.null_ || ExternRefType.undefined => null,
-    ExternRefType.boolean => toDartBool(ref),
-    ExternRefType.number => toDartNumber(ref),
+    ExternRefType.boolean => _toDartBoolUnchecked(ref),
+    ExternRefType.number => _toDartDoubleUnchecked(ref),
     ExternRefType.string => JSStringImpl.fromRefUnchecked(ref),
     ExternRefType.array => toDartList(ref),
-    ExternRefType.int8Array => js_types.JSInt8ArrayImpl.fromArrayRefUnchecked(
-      ref,
-    ),
-    ExternRefType.uint8Array => js_types.JSUint8ArrayImpl.fromArrayRefUnchecked(
-      ref,
-    ),
+    ExternRefType.int8Array => js_types.JSInt8ArrayImpl.fromRefUnchecked(ref),
+    ExternRefType.uint8Array => js_types.JSUint8ArrayImpl.fromRefUnchecked(ref),
     ExternRefType.uint8ClampedArray =>
-      js_types.JSUint8ClampedArrayImpl.fromArrayRefUnchecked(ref),
-    ExternRefType.int16Array => js_types.JSInt16ArrayImpl.fromArrayRefUnchecked(
+      js_types.JSUint8ClampedArrayImpl.fromRefUnchecked(ref),
+    ExternRefType.int16Array => js_types.JSInt16ArrayImpl.fromRefUnchecked(ref),
+    ExternRefType.uint16Array => js_types.JSUint16ArrayImpl.fromRefUnchecked(
       ref,
     ),
-    ExternRefType.uint16Array =>
-      js_types.JSUint16ArrayImpl.fromArrayRefUnchecked(ref),
-    ExternRefType.int32Array => js_types.JSInt32ArrayImpl.fromArrayRefUnchecked(
+    ExternRefType.int32Array => js_types.JSInt32ArrayImpl.fromRefUnchecked(ref),
+    ExternRefType.uint32Array => js_types.JSUint32ArrayImpl.fromRefUnchecked(
+      ref,
+    ),
+    ExternRefType.float32Array => js_types.JSFloat32ArrayImpl.fromRefUnchecked(
+      ref,
+    ),
+    ExternRefType.float64Array => js_types.JSFloat64ArrayImpl.fromRefUnchecked(
       ref,
     ),
-    ExternRefType.uint32Array =>
-      js_types.JSUint32ArrayImpl.fromArrayRefUnchecked(ref),
-    ExternRefType.float32Array =>
-      js_types.JSFloat32ArrayImpl.fromArrayRefUnchecked(ref),
-    ExternRefType.float64Array =>
-      js_types.JSFloat64ArrayImpl.fromArrayRefUnchecked(ref),
     ExternRefType.arrayBuffer || ExternRefType.sharedArrayBuffer =>
       js_types.JSArrayBufferImpl.fromRefUnchecked(ref),
     ExternRefType.dataView => js_types.JSDataViewImpl.fromRefUnchecked(ref),
@@ -581,18 +649,6 @@ Object? dartifyRaw(WasmExternRef? ref, [int? refType]) {
   };
 }
 
-@pragma('wasm:entry-point')
-int dartifyInt(WasmExternRef? ref) {
-  final dartDouble = toDartNumber(ref);
-  if (dartDouble.isFinite) {
-    final dartInt = dartDouble.toInt();
-    if (dartInt.toDouble() == dartDouble) {
-      return dartInt;
-    }
-  }
-  throw ArgumentError('JS value is not integer');
-}
-
 List<double> jsFloatTypedArrayToDartFloatTypedData(
   WasmExternRef? ref,
   List<double> makeTypedData(int size),
@@ -600,7 +656,7 @@ List<double> jsFloatTypedArrayToDartFloatTypedData(
   int length = objectLength(ref);
   List<double> list = makeTypedData(length);
   for (int i = 0; i < length; i++) {
-    list[i] = toDartNumber(objectReadIndex(ref, i));
+    list[i] = toDartDouble(objectReadIndex(ref, i));
   }
   return list;
 }
@@ -612,7 +668,7 @@ List<int> jsIntTypedArrayToDartIntTypedData(
   int length = objectLength(ref);
   List<int> list = makeTypedData(length);
   for (int i = 0; i < length; i++) {
-    list[i] = toDartNumber(objectReadIndex(ref, i)).toInt();
+    list[i] = toDartDouble(objectReadIndex(ref, i)).toInt();
   }
   return list;
 }
@@ -673,6 +729,12 @@ List<Object?> toDartList(WasmExternRef? ref) => List<Object?>.generate(
   (int n) => dartifyRaw(objectReadIndex(ref, n)),
 );
 
+@pragma('wasm:entry-point')
+List<Object?>? toDartNullableList(WasmExternRef? ref) {
+  if (ref.isNull || isJSUndefined(ref)) return null;
+  return toDartList(ref);
+}
+
 // These two trivial helpers are needed to work around an issue with tearing off
 // functions that take / return [WasmExternRef].
 bool _isDartFunctionWrapped<F extends Function>(F f) =>
diff --git a/sdk/lib/_internal/wasm/lib/js_interop_patch.dart b/sdk/lib/_internal/wasm/lib/js_interop_patch.dart
index 0b5d97c586d..6cfec6fbf73 100644
--- a/sdk/lib/_internal/wasm/lib/js_interop_patch.dart
+++ b/sdk/lib/_internal/wasm/lib/js_interop_patch.dart
@@ -374,7 +374,7 @@ extension ByteDataToJSDataView on ByteData {
 @patch
 extension JSInt8ArrayToInt8List on JSInt8Array {
   @patch
-  Int8List get toDart => js_types.JSInt8ArrayImpl.fromArrayRef(toExternRef);
+  Int8List get toDart => js_types.JSInt8ArrayImpl.fromRef(toExternRef);
 }
 
 @patch
@@ -397,7 +397,7 @@ extension Int8ListToJSInt8Array on Int8List {
 @patch
 extension JSUint8ArrayToUint8List on JSUint8Array {
   @patch
-  Uint8List get toDart => js_types.JSUint8ArrayImpl.fromArrayRef(toExternRef);
+  Uint8List get toDart => js_types.JSUint8ArrayImpl.fromRef(toExternRef);
 }
 
 @patch
@@ -421,7 +421,7 @@ extension Uint8ListToJSUint8Array on Uint8List {
 extension JSUint8ClampedArrayToUint8ClampedList on JSUint8ClampedArray {
   @patch
   Uint8ClampedList get toDart =>
-      js_types.JSUint8ClampedArrayImpl.fromArrayRef(toExternRef);
+      js_types.JSUint8ClampedArrayImpl.fromRef(toExternRef);
 }
 
 @patch
@@ -444,7 +444,7 @@ extension Uint8ClampedListToJSUint8ClampedArray on Uint8ClampedList {
 @patch
 extension JSInt16ArrayToInt16List on JSInt16Array {
   @patch
-  Int16List get toDart => js_types.JSInt16ArrayImpl.fromArrayRef(toExternRef);
+  Int16List get toDart => js_types.JSInt16ArrayImpl.fromRef(toExternRef);
 }
 
 @patch
@@ -467,7 +467,7 @@ extension Int16ListToJSInt16Array on Int16List {
 @patch
 extension JSUint16ArrayToUint16List on JSUint16Array {
   @patch
-  Uint16List get toDart => js_types.JSUint16ArrayImpl.fromArrayRef(toExternRef);
+  Uint16List get toDart => js_types.JSUint16ArrayImpl.fromRef(toExternRef);
 }
 
 @patch
@@ -490,7 +490,7 @@ extension Uint16ListToJSUint16Array on Uint16List {
 @patch
 extension JSInt32ArrayToInt32List on JSInt32Array {
   @patch
-  Int32List get toDart => js_types.JSInt32ArrayImpl.fromArrayRef(toExternRef);
+  Int32List get toDart => js_types.JSInt32ArrayImpl.fromRef(toExternRef);
 }
 
 @patch
@@ -513,7 +513,7 @@ extension Int32ListToJSInt32Array on Int32List {
 @patch
 extension JSUint32ArrayToUint32List on JSUint32Array {
   @patch
-  Uint32List get toDart => js_types.JSUint32ArrayImpl.fromArrayRef(toExternRef);
+  Uint32List get toDart => js_types.JSUint32ArrayImpl.fromRef(toExternRef);
 }
 
 @patch
@@ -536,8 +536,7 @@ extension Uint32ListToJSUint32Array on Uint32List {
 @patch
 extension JSFloat32ArrayToFloat32List on JSFloat32Array {
   @patch
-  Float32List get toDart =>
-      js_types.JSFloat32ArrayImpl.fromArrayRef(toExternRef);
+  Float32List get toDart => js_types.JSFloat32ArrayImpl.fromRef(toExternRef);
 }
 
 @patch
@@ -560,8 +559,7 @@ extension Float32ListToJSFloat32Array on Float32List {
 @patch
 extension JSFloat64ArrayToFloat64List on JSFloat64Array {
   @patch
-  Float64List get toDart =>
-      js_types.JSFloat64ArrayImpl.fromArrayRef(toExternRef);
+  Float64List get toDart => js_types.JSFloat64ArrayImpl.fromRef(toExternRef);
 }
 
 @patch
@@ -610,18 +608,10 @@ extension ListToJSArray<T extends JSAny?> on List<T> {
 @patch
 extension JSNumberToNumber on JSNumber {
   @patch
-  double get toDartDouble => toDartNumber(toExternRef);
+  double get toDartDouble => js_helper.toDartDouble(toExternRef);
 
   @patch
-  int get toDartInt {
-    final number = toDartNumber(toExternRef);
-    final intVal = number.toInt();
-    if (number == intVal) {
-      return intVal;
-    } else {
-      throw 'Expected integer value, but was not integer.';
-    }
-  }
+  int get toDartInt => js_helper.toDartInt(toExternRef);
 }
 
 @patch
diff --git a/sdk/lib/_internal/wasm/lib/js_string.dart b/sdk/lib/_internal/wasm/lib/js_string.dart
index 8809e8ff667..c482f854ac8 100644
--- a/sdk/lib/_internal/wasm/lib/js_string.dart
+++ b/sdk/lib/_internal/wasm/lib/js_string.dart
@@ -40,6 +40,7 @@ final class JSStringImpl implements String, StringUncheckedOperationsBase {
     assert(_checkRefType(_ref));
   }
 
+  @pragma('wasm:entry-point')
   factory JSStringImpl.fromRef(WasmExternRef? ref) {
     if (!_checkRefType(ref)) {
       throw minify
@@ -49,6 +50,20 @@ final class JSStringImpl implements String, StringUncheckedOperationsBase {
     return JSStringImpl.fromRefUnchecked(ref);
   }
 
+  @pragma('wasm:entry-point')
+  static JSStringImpl? fromRefNullable(WasmExternRef? ref) {
+    final int refType = js.JS<WasmI32>('''o => {
+        if (o === null || o === undefined) return 0;
+        if (typeof(o) === 'string') return 1;
+        return 2;
+      }''', ref).toIntUnsigned();
+    if (refType == 0) return null;
+    if (refType == 1) return JSStringImpl.fromRefUnchecked(ref);
+    throw minify
+        ? ArgumentError()
+        : ArgumentError("JS reference is not a string");
+  }
+
   @pragma("wasm:prefer-inline")
   static String? box(WasmExternRef? ref) =>
       js.isDartNull(ref) ? null : JSStringImpl.fromRefUnchecked(ref);
diff --git a/sdk/lib/_internal/wasm/lib/js_typed_array.dart b/sdk/lib/_internal/wasm/lib/js_typed_array.dart
index 3d8cc457e58..6c46cdd05d8 100644
--- a/sdk/lib/_internal/wasm/lib/js_typed_array.dart
+++ b/sdk/lib/_internal/wasm/lib/js_typed_array.dart
@@ -9,9 +9,10 @@ part of "dart:_js_types";
 ///
 /// Constants are preferred over enums for performance.
 abstract final class _ArrayBufferType {
-  static const int arrayBuffer = 0;
-  static const int sharedArrayBuffer = 1;
-  static const int unknown = 2;
+  static const int nullOrUndefined = 0;
+  static const int arrayBuffer = 1;
+  static const int sharedArrayBuffer = 2;
+  static const int unknown = 3;
 }
 
 /// A JS `ArrayBuffer` or `SharedArrayBuffer`.
@@ -23,16 +24,17 @@ final class JSArrayBufferImpl implements ByteBuffer {
 
   late int _refType = _getRefType(_ref);
 
-  static int _getRefType(WasmExternRef? _ref) =>
+  static int _getRefType(WasmExternRef? ref) =>
       // Feature check for `SharedArrayBuffer` before doing a type-check.
       js.JS<WasmI32>('''o => {
-          if (o instanceof ArrayBuffer) return 0;
+          if (o === null || o === undefined) return 0;
+          if (o instanceof ArrayBuffer) return 1;
           if (globalThis.SharedArrayBuffer !== undefined &&
               o instanceof SharedArrayBuffer) {
-            return 1;
+            return 2;
           }
-          return 2;
-        }''', _ref).toIntUnsigned();
+          return 3;
+        }''', ref).toIntUnsigned();
 
   bool get isArrayBuffer => _refType == _ArrayBufferType.arrayBuffer;
 
@@ -53,6 +55,14 @@ final class JSArrayBufferImpl implements ByteBuffer {
     return JSArrayBufferImpl.fromRefUnchecked(ref);
   }
 
+  static JSArrayBufferImpl? fromRefNullable(WasmExternRef? ref) {
+    final refType = _getRefType(ref);
+    if (refType == _ArrayBufferType.nullOrUndefined) return null;
+    if (refType == _ArrayBufferType.unknown)
+      return _throwConversionFailureError("ByteBuffer");
+    return JSArrayBufferImpl.fromRefUnchecked(ref);
+  }
+
   @pragma("wasm:prefer-inline")
   WasmExternRef? get toExternRef => _ref;
 
@@ -286,11 +296,14 @@ final class JSDataViewImpl implements ByteData {
 
   final bool _immutable;
 
-  static bool _checkRefType(WasmExternRef? ref) =>
-      js.JS<bool>('o => o instanceof DataView', ref);
+  static int _getRefType(WasmExternRef? ref) => js.JS<WasmI32>('''o => {
+          if (o === null || o === undefined) return 0;
+          if (o instanceof DataView) return 1;
+          return 2;
+        }''', ref).toIntUnsigned();
 
   JSDataViewImpl._(this._ref, this.lengthInBytes, this._immutable) {
-    assert(_checkRefType(_ref));
+    assert(_getRefType(_ref) == 1);
   }
 
   JSDataViewImpl(this.lengthInBytes)
@@ -302,12 +315,18 @@ final class JSDataViewImpl implements ByteData {
       _immutable = false;
 
   factory JSDataViewImpl.fromRef(WasmExternRef? ref) {
-    if (!_checkRefType(ref)) {
-      return _throwConversionFailureError("ByteData");
-    }
+    final refType = _getRefType(ref);
+    if (refType != 1) return _throwConversionFailureError("ByteData");
     return JSDataViewImpl.fromRefUnchecked(ref);
   }
 
+  static JSDataViewImpl? fromRefNullable(WasmExternRef? ref) {
+    final refType = _getRefType(ref);
+    if (refType == 0) return null;
+    if (refType == 2) return JSDataViewImpl.fromRefUnchecked(ref);
+    return _throwConversionFailureError("ByteData");
+  }
+
   JSDataViewImpl.immutable(this._ref, this.lengthInBytes) : _immutable = true;
 
   factory JSDataViewImpl.view(
@@ -825,19 +844,29 @@ final class JSUint8ArrayImpl extends JSIntegerArrayBase
   factory JSUint8ArrayImpl(int length) =>
       JSUint8ArrayImpl._(_newDataView(length));
 
-  static bool _checkArrayRefType(WasmExternRef? ref) =>
-      js.JS<bool>('o => o instanceof Uint8Array', ref);
+  static int _getRefType(WasmExternRef? ref) => js.JS<WasmI32>('''o => {
+          if (o === null || o === undefined) return 0;
+          if (o instanceof Uint8Array) return 1;
+          return 2;
+        }''', ref).toIntUnsigned();
 
-  factory JSUint8ArrayImpl.fromArrayRefUnchecked(WasmExternRef? ref) {
-    _checkArrayRefType(ref);
+  factory JSUint8ArrayImpl.fromRefUnchecked(WasmExternRef? ref) {
+    assert(_getRefType(ref) == 1);
     return JSUint8ArrayImpl._(_dataViewFromJSArray(ref), ref);
   }
 
-  factory JSUint8ArrayImpl.fromArrayRef(WasmExternRef? ref) {
-    if (!_checkArrayRefType(ref)) {
+  factory JSUint8ArrayImpl.fromRef(WasmExternRef? ref) {
+    if (_getRefType(ref) != 1) {
       return _throwConversionFailureError("Uint8List");
     }
-    return JSUint8ArrayImpl.fromArrayRefUnchecked(ref);
+    return JSUint8ArrayImpl.fromRefUnchecked(ref);
+  }
+
+  static JSUint8ArrayImpl? fromRefNullable(WasmExternRef? ref) {
+    final refType = _getRefType(ref);
+    if (refType == 0) return null;
+    if (refType == 1) return JSUint8ArrayImpl.fromRefUnchecked(ref);
+    return _throwConversionFailureError("Uint8List");
   }
 
   factory JSUint8ArrayImpl.view(
@@ -931,19 +960,29 @@ final class JSInt8ArrayImpl extends JSIntegerArrayBase
   factory JSInt8ArrayImpl(int length) =>
       JSInt8ArrayImpl._(_newDataView(length));
 
-  static bool _checkArrayRefType(WasmExternRef? ref) =>
-      js.JS<bool>('o => o instanceof Int8Array', ref);
+  static int _getRefType(WasmExternRef? ref) => js.JS<WasmI32>('''o => {
+          if (o === null || o === undefined) return 0;
+          if (o instanceof Int8Array) return 1;
+          return 2;
+        }''', ref).toIntUnsigned();
 
-  factory JSInt8ArrayImpl.fromArrayRefUnchecked(WasmExternRef? ref) {
-    assert(_checkArrayRefType(ref));
+  factory JSInt8ArrayImpl.fromRefUnchecked(WasmExternRef? ref) {
+    assert(_getRefType(ref) == 1);
     return JSInt8ArrayImpl._(_dataViewFromJSArray(ref), ref);
   }
 
-  factory JSInt8ArrayImpl.fromArrayRef(WasmExternRef? ref) {
-    if (!_checkArrayRefType(ref)) {
+  factory JSInt8ArrayImpl.fromRef(WasmExternRef? ref) {
+    if (_getRefType(ref) != 1) {
       return _throwConversionFailureError("Int8List");
     }
-    return JSInt8ArrayImpl.fromArrayRefUnchecked(ref);
+    return JSInt8ArrayImpl.fromRefUnchecked(ref);
+  }
+
+  static JSInt8ArrayImpl? fromRefNullable(WasmExternRef? ref) {
+    final refType = _getRefType(ref);
+    if (refType == 0) return null;
+    if (refType == 1) return JSInt8ArrayImpl.fromRefUnchecked(ref);
+    return _throwConversionFailureError("Int8List");
   }
 
   factory JSInt8ArrayImpl.view(
@@ -1042,16 +1081,26 @@ final class JSUint8ClampedArrayImpl extends JSIntegerArrayBase
   static bool _checkArrayRefType(WasmExternRef? ref) =>
       js.JS<bool>('o => o instanceof Uint8ClampedArray', ref);
 
-  factory JSUint8ClampedArrayImpl.fromArrayRefUnchecked(WasmExternRef? ref) {
+  factory JSUint8ClampedArrayImpl.fromRefUnchecked(WasmExternRef? ref) {
     assert(_checkArrayRefType(ref));
     return JSUint8ClampedArrayImpl._(_dataViewFromJSArray(ref), ref);
   }
 
-  factory JSUint8ClampedArrayImpl.fromArrayRef(WasmExternRef? ref) {
+  factory JSUint8ClampedArrayImpl.fromRef(WasmExternRef? ref) {
     if (!_checkArrayRefType(ref)) {
       return _throwConversionFailureError("Uint8ClampedList");
     }
-    return JSUint8ClampedArrayImpl.fromArrayRefUnchecked(ref);
+    return JSUint8ClampedArrayImpl.fromRefUnchecked(ref);
+  }
+
+  static JSUint8ClampedArrayImpl? fromRefNullable(WasmExternRef? ref) {
+    if (!_checkArrayRefType(ref)) {
+      if (ref.isNull) {
+        return null;
+      }
+      return _throwConversionFailureError("Uint8ClampedList");
+    }
+    return JSUint8ClampedArrayImpl.fromRefUnchecked(ref);
   }
 
   factory JSUint8ClampedArrayImpl.view(
@@ -1134,16 +1183,26 @@ final class JSUint16ArrayImpl extends JSIntegerArrayBase
   static bool _checkArrayRefType(WasmExternRef? ref) =>
       js.JS<bool>('o => o instanceof Uint16Array', ref);
 
-  factory JSUint16ArrayImpl.fromArrayRefUnchecked(WasmExternRef? ref) {
+  factory JSUint16ArrayImpl.fromRefUnchecked(WasmExternRef? ref) {
     assert(_checkArrayRefType(ref));
     return JSUint16ArrayImpl._(_dataViewFromJSArray(ref), ref);
   }
 
-  factory JSUint16ArrayImpl.fromArrayRef(WasmExternRef? ref) {
+  factory JSUint16ArrayImpl.fromRef(WasmExternRef? ref) {
     if (!_checkArrayRefType(ref)) {
       return _throwConversionFailureError("Uint16List");
     }
-    return JSUint16ArrayImpl.fromArrayRefUnchecked(ref);
+    return JSUint16ArrayImpl.fromRefUnchecked(ref);
+  }
+
+  static JSUint16ArrayImpl? fromRefNullable(WasmExternRef? ref) {
+    if (!_checkArrayRefType(ref)) {
+      if (ref.isNull) {
+        return null;
+      }
+      return _throwConversionFailureError("Uint16List");
+    }
+    return JSUint16ArrayImpl.fromRefUnchecked(ref);
   }
 
   factory JSUint16ArrayImpl.view(
@@ -1247,16 +1306,26 @@ final class JSInt16ArrayImpl extends JSIntegerArrayBase
   static bool _checkArrayRefType(WasmExternRef? ref) =>
       js.JS<bool>('o => o instanceof Int16Array', ref);
 
-  factory JSInt16ArrayImpl.fromArrayRefUnchecked(WasmExternRef? ref) {
+  factory JSInt16ArrayImpl.fromRefUnchecked(WasmExternRef? ref) {
     assert(_checkArrayRefType(ref));
     return JSInt16ArrayImpl._(_dataViewFromJSArray(ref), ref);
   }
 
-  factory JSInt16ArrayImpl.fromArrayRef(WasmExternRef? ref) {
+  factory JSInt16ArrayImpl.fromRef(WasmExternRef? ref) {
     if (!_checkArrayRefType(ref)) {
       return _throwConversionFailureError("Int16List");
     }
-    return JSInt16ArrayImpl.fromArrayRefUnchecked(ref);
+    return JSInt16ArrayImpl.fromRefUnchecked(ref);
+  }
+
+  static JSInt16ArrayImpl? fromRefNullable(WasmExternRef? ref) {
+    if (!_checkArrayRefType(ref)) {
+      if (ref.isNull) {
+        return null;
+      }
+      return _throwConversionFailureError("Int16List");
+    }
+    return JSInt16ArrayImpl.fromRefUnchecked(ref);
   }
 
   factory JSInt16ArrayImpl.view(
@@ -1357,19 +1426,29 @@ final class JSUint32ArrayImpl extends JSIntegerArrayBase
   factory JSUint32ArrayImpl(int length) =>
       JSUint32ArrayImpl._(_newDataView(length * 4));
 
-  static bool _checkArrayRefType(WasmExternRef? ref) =>
-      js.JS<bool>('o => o instanceof Uint32Array', ref);
+  static int _getRefType(WasmExternRef? ref) => js.JS<WasmI32>('''o => {
+          if (o === null || o === undefined) return 0;
+          if (o instanceof Uint32Array) return 1;
+          return 2;
+        }''', ref).toIntUnsigned();
 
-  factory JSUint32ArrayImpl.fromArrayRefUnchecked(WasmExternRef? ref) {
-    assert(_checkArrayRefType(ref));
+  factory JSUint32ArrayImpl.fromRefUnchecked(WasmExternRef? ref) {
+    assert(_getRefType(ref) == 1);
     return JSUint32ArrayImpl._(_dataViewFromJSArray(ref), ref);
   }
 
-  factory JSUint32ArrayImpl.fromArrayRef(WasmExternRef? ref) {
-    if (!_checkArrayRefType(ref)) {
+  factory JSUint32ArrayImpl.fromRef(WasmExternRef? ref) {
+    if (_getRefType(ref) != 1) {
       return _throwConversionFailureError("Uint32List");
     }
-    return JSUint32ArrayImpl.fromArrayRefUnchecked(ref);
+    return JSUint32ArrayImpl.fromRefUnchecked(ref);
+  }
+
+  static JSUint32ArrayImpl? fromRefNullable(WasmExternRef? ref) {
+    final refType = _getRefType(ref);
+    if (refType == 0) return null;
+    if (refType == 1) return JSUint32ArrayImpl.fromRefUnchecked(ref);
+    return _throwConversionFailureError("Uint32List");
   }
 
   factory JSUint32ArrayImpl.view(
@@ -1470,19 +1549,29 @@ final class JSInt32ArrayImpl extends JSIntegerArrayBase
   factory JSInt32ArrayImpl(int length) =>
       JSInt32ArrayImpl._(_newDataView(length * 4));
 
-  static bool _checkArrayRefType(WasmExternRef? ref) =>
-      js.JS<bool>('o => o instanceof Int32Array', ref);
+  static int _getRefType(WasmExternRef? ref) => js.JS<WasmI32>('''o => {
+          if (o === null || o === undefined) return 0;
+          if (o instanceof Int32Array) return 1;
+          return 2;
+        }''', ref).toIntUnsigned();
 
-  factory JSInt32ArrayImpl.fromArrayRefUnchecked(WasmExternRef? ref) {
-    assert(_checkArrayRefType(ref));
+  factory JSInt32ArrayImpl.fromRefUnchecked(WasmExternRef? ref) {
+    assert(_getRefType(ref) == 1);
     return JSInt32ArrayImpl._(_dataViewFromJSArray(ref), ref);
   }
 
-  factory JSInt32ArrayImpl.fromArrayRef(WasmExternRef? ref) {
-    if (!_checkArrayRefType(ref)) {
+  factory JSInt32ArrayImpl.fromRef(WasmExternRef? ref) {
+    if (_getRefType(ref) != 1) {
       return _throwConversionFailureError("Int32List");
     }
-    return JSInt32ArrayImpl.fromArrayRefUnchecked(ref);
+    return JSInt32ArrayImpl.fromRefUnchecked(ref);
+  }
+
+  static JSInt32ArrayImpl? fromRefNullable(WasmExternRef? ref) {
+    final refType = _getRefType(ref);
+    if (refType == 0) return null;
+    if (refType == 1) return JSInt32ArrayImpl.fromRefUnchecked(ref);
+    return _throwConversionFailureError("Int32List");
   }
 
   factory JSInt32ArrayImpl.view(
@@ -2222,19 +2311,29 @@ final class JSFloat32ArrayImpl extends JSFloatArrayBase
   factory JSFloat32ArrayImpl(int length) =>
       JSFloat32ArrayImpl._(_newDataView(length * 4));
 
-  static bool _checkArrayRefType(WasmExternRef? ref) =>
-      js.JS<bool>('o => o instanceof Float32Array', ref);
+  static int _getRefType(WasmExternRef? ref) => js.JS<WasmI32>('''o => {
+          if (o === null || o === undefined) return 0;
+          if (o instanceof Float32Array) return 1;
+          return 2;
+        }''', ref).toIntUnsigned();
 
-  factory JSFloat32ArrayImpl.fromArrayRefUnchecked(WasmExternRef? ref) {
-    assert(_checkArrayRefType(ref));
+  factory JSFloat32ArrayImpl.fromRefUnchecked(WasmExternRef? ref) {
+    assert(_getRefType(ref) == 1);
     return JSFloat32ArrayImpl._(_dataViewFromJSArray(ref), ref);
   }
 
-  factory JSFloat32ArrayImpl.fromArrayRef(WasmExternRef? ref) {
-    if (!_checkArrayRefType(ref)) {
+  factory JSFloat32ArrayImpl.fromRef(WasmExternRef? ref) {
+    if (_getRefType(ref) != 1) {
       return _throwConversionFailureError("Float32List");
     }
-    return JSFloat32ArrayImpl.fromArrayRefUnchecked(ref);
+    return JSFloat32ArrayImpl.fromRefUnchecked(ref);
+  }
+
+  static JSFloat32ArrayImpl? fromRefNullable(WasmExternRef? ref) {
+    final refType = _getRefType(ref);
+    if (refType == 0) return null;
+    if (refType == 1) return JSFloat32ArrayImpl.fromRefUnchecked(ref);
+    return _throwConversionFailureError("Float32List");
   }
 
   factory JSFloat32ArrayImpl.view(
@@ -2336,19 +2435,29 @@ final class JSFloat64ArrayImpl extends JSFloatArrayBase
   factory JSFloat64ArrayImpl(int length) =>
       JSFloat64ArrayImpl._(_newDataView(length * 8));
 
-  static bool _checkArrayRefType(WasmExternRef? ref) =>
-      js.JS<bool>('o => o instanceof Float64Array', ref);
+  static int _getRefType(WasmExternRef? ref) => js.JS<WasmI32>('''o => {
+          if (o === null || o === undefined) return 0;
+          if (o instanceof Float64Array) return 1;
+          return 2;
+        }''', ref).toIntUnsigned();
 
-  factory JSFloat64ArrayImpl.fromArrayRefUnchecked(WasmExternRef? ref) {
-    assert(_checkArrayRefType(ref));
+  factory JSFloat64ArrayImpl.fromRefUnchecked(WasmExternRef? ref) {
+    assert(_getRefType(ref) == 1);
     return JSFloat64ArrayImpl._(_dataViewFromJSArray(ref), ref);
   }
 
-  factory JSFloat64ArrayImpl.fromArrayRef(WasmExternRef? ref) {
-    if (!_checkArrayRefType(ref)) {
+  factory JSFloat64ArrayImpl.fromRef(WasmExternRef? ref) {
+    if (_getRefType(ref) != 1) {
       return _throwConversionFailureError("Float64List");
     }
-    return JSFloat64ArrayImpl.fromArrayRefUnchecked(ref);
+    return JSFloat64ArrayImpl.fromRefUnchecked(ref);
+  }
+
+  static JSFloat64ArrayImpl? fromRefNullable(WasmExternRef? ref) {
+    final refType = _getRefType(ref);
+    if (refType == 0) return null;
+    if (refType == 1) return JSFloat64ArrayImpl.fromRefUnchecked(ref);
+    return _throwConversionFailureError("Float64List");
   }
 
   factory JSFloat64ArrayImpl.view(
diff --git a/tests/web/wasm/js_interop_type_tests_test.dart b/tests/web/wasm/js_interop_type_tests_test.dart
index 0c6af8bd946..2d4cf25fb42 100644
--- a/tests/web/wasm/js_interop_type_tests_test.dart
+++ b/tests/web/wasm/js_interop_type_tests_test.dart
@@ -15,47 +15,45 @@ import 'package:expect/expect.dart';
 
 void main() {
   Expect.throws<ArgumentError>(
-    () => JSInt8ArrayImpl.fromArrayRef(
+    () =>
+        JSInt8ArrayImpl.fromRef(JS<WasmExternRef?>('() => new Uint8Array(10)')),
+  );
+  Expect.throws<ArgumentError>(
+    () =>
+        JSUint8ArrayImpl.fromRef(JS<WasmExternRef?>('() => new Int8Array(10)')),
+  );
+  Expect.throws<ArgumentError>(
+    () => JSUint8ClampedArrayImpl.fromRef(
       JS<WasmExternRef?>('() => new Uint8Array(10)'),
     ),
   );
   Expect.throws<ArgumentError>(
-    () => JSUint8ArrayImpl.fromArrayRef(
-      JS<WasmExternRef?>('() => new Int8Array(10)'),
-    ),
-  );
-  Expect.throws<ArgumentError>(
-    () => JSUint8ClampedArrayImpl.fromArrayRef(
-      JS<WasmExternRef?>('() => new Uint8Array(10)'),
-    ),
-  );
-  Expect.throws<ArgumentError>(
-    () => JSInt16ArrayImpl.fromArrayRef(
+    () => JSInt16ArrayImpl.fromRef(
       JS<WasmExternRef?>('() => new Uint16Array(10)'),
     ),
   );
   Expect.throws<ArgumentError>(
-    () => JSUint16ArrayImpl.fromArrayRef(
+    () => JSUint16ArrayImpl.fromRef(
       JS<WasmExternRef?>('() => new Int16Array(10)'),
     ),
   );
   Expect.throws<ArgumentError>(
-    () => JSInt32ArrayImpl.fromArrayRef(
+    () => JSInt32ArrayImpl.fromRef(
       JS<WasmExternRef?>('() => new Uint32Array(10)'),
     ),
   );
   Expect.throws<ArgumentError>(
-    () => JSUint32ArrayImpl.fromArrayRef(
+    () => JSUint32ArrayImpl.fromRef(
       JS<WasmExternRef?>('() => new Int32Array(10)'),
     ),
   );
   Expect.throws<ArgumentError>(
-    () => JSFloat32ArrayImpl.fromArrayRef(
+    () => JSFloat32ArrayImpl.fromRef(
       JS<WasmExternRef?>('() => new Float64Array(10)'),
     ),
   );
   Expect.throws<ArgumentError>(
-    () => JSFloat64ArrayImpl.fromArrayRef(
+    () => JSFloat64ArrayImpl.fromRef(
       JS<WasmExternRef?>('() => new Float32Array(10)'),
     ),
   );