Laravel app.js and bootstrap.js are not included?

I installed a fresh Laravel 5.8 and included the

<script src=""></script>

at the bottom of welcome.blade.php. To avoid error, set a div with id=app.

If I write alert(123) inside public/js/app.js it will be alerted when I visit this page and it is ok. I noticed that in line 60329 of public/js/app.js it has

webpack_require(/*! C:\xampp\htdocs\br1\resources\js\app.js */"./resources/js/app.js");

sounds it includes the resources\js\app.js and resources\js\app.js includes resources\js\bootstrap.js

When I write the alert(22) in resources\js\app.js or resources\js\bootstrap.js nothing will be alerted while it must alert something.

Thanks in advance.

via Chebli Mohamed