LibTest/js_interop/FunctionToJSExportedDartFunction/toJSCaptureThis_A01_t09.dart

// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

/// @assertion JSExportedDartFunction get toJSCaptureThis
/// A callable JavaScript function that wraps this [Function] and captures the
/// `this` value when called.
///
/// Identical to `toJS`, except the resulting [JSExportedDartFunction] will pass
/// `this` from JavaScript as the first argument to the converted [Function].
/// Any [Function] that is converted with this member should take in an extra
/// parameter at the beginning of the parameter list to handle this.
///
/// @description Check that this property returns a JavaScript function that
/// wraps this [Function] and captures the `this` value when called. Check that
/// `null` can be passed as the value of `this`.
/// @author sgrekhov22@gmail.com

import 'dart:js_interop';
import 'dart:js_interop_unsafe';
import '../../../Utils/expect.dart';

void foo(JSAny? pThis) {
  if (isDart2JS && !isDDC) {
    // Test runner runs `dart2js` tests in non-strict mode. In this case
    // (see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/call#parameters)
    // `null` is replaced by the global object.
    Expect.equals(globalContext, pThis);
  }
  if (isWasm || isDDC) {
    // `dart2wasm` and ddc tests are run in the strict mode.
    Expect.isNull(pThis);
  }
}

main() {
  globalContext["jsFoo"] = foo.toJSCaptureThis;
  JSFunction jsFoo = globalContext["jsFoo"] as JSFunction;
  jsFoo.callAsFunction(null);
}