What is the method for invoking a Dart asynchronous function from JavaScript?

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To invoke a Dart asynchronous function from JavaScript, you can use the JavaScript Interop feature provided by the Dart language. Here is an example code snippet:

1. First, import the 'dart:js' library in your Dart code:

import 'dart:js' as js;

1. Define your asynchronous function in Dart:

Future<String> myAsyncFunc(int param) async {
  // Some asynchronous operation
  return 'result';
}

1. Expose your function as a global JavaScript variable:

// Add this line after defining your function
js.context['myAsyncFunc'] = myAsyncFunc;

1. Finally, you can call your Dart function from JavaScript as follows:

// In JavaScript:
const result = await window.dartInterop.myAsyncFunc(123);
console.log(result);

Note that you may need to wrap the call to your Dart function with a 'Promise' object in order to handle the asynchronous result.