How to inject a window variable in a storybook?

The window you're trying to access is the iframe preview. Try to access the window from outside the iframe, the Storybook window.

window.parent.window.GLOBAL

I can add a preview-head.html file in the __stories__ directory.

Inside which I have javascript like this:

<script>
  var data = { };
  window.GLOBAL = {
    data: data
  };  
 </script>

Documentation

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