How to injest javascript in

742 Views Asked by Valentin Vignal At 06 November 2025 at 14:18

I'm working on a Flutter web project. The web/index.html file is injecting a JavaScript script which could be simplified as:

<script>
  window['dataLayer'] = [];
</script>

So in my flutter code, I can do:

@JS()
import 'package:js/js.dart';

@JS('dataLayer.push')
external void push(data);

push(myData);

to push myData in the window.dataLayer array.

However, in the tests, when I'm running

flutter test --platform chrome

I'm getting the error

TypeError: Cannot read properties of undefined (reading 'push')

when I call

push(myData);

because window['dataLayer'] has never been created.

How can I inject some javascript scripts the same way I can do in the index.html?

Original Q&A

There are 1 best solutions below

Valentin Vignal On 06 May 2022 at 01:19 BEST ANSWER

It is possible to load a custom HTML file while running the tests, see the instructions of the package test.

If your test file name is folder/my_test.dart, then you can create a html file named (folder/my_test.html):

<!doctype html>
<html>

<head>
  <title>Custom HTML file title</title>
  <link rel="x-dart-test" href="my_test.dart">
  <script src="packages/test/dart.js"></script>
  <script>
    window['dataLayer'] = [];
  </script>
</head>

</html>

See this StackOverflow question.

and then you can run

dart test --platform chrome

However, this is only supported with dart test and not flutter test, see this issue. In it, they recommend writing an integration test instead.

How to injest javascript in

There are 1 best solutions below

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