Get Auth::user()->id in javascript

Pass the data to Javascript in your Blade template:

<script>
  window.userID = {{ auth()->id() }};
</script>

Now you have a userID property on the window Object. You could, of course, define a different structure if your app needs other data shared from PHP, but the general idea would be the same.

This is a Laracasts package that was the subject of a video tutorial a number of years ago - it supports Laravel 8; but it should not be necessary unless you are passing a lot of data dynamically to the frontend:

https://github.com/laracasts/PHP-Vars-To-Js-Transformer

It depends on where the scripts are relative to each other in the DOM.

@the beginner Why are you trying to get sensitive server-side data like the authenticated user, into your JavaScript? What are you wanting to do with the authenticated user object once you have it?