I would assume that you want to load your javascript file from a relative path (relative to your html page) rather than an absolute path. Absolute paths start with a / (slash).
Try
<script src="https://stackoverflow.com/questions/40283606/js/script1.js"></script>
To debug it right click your page and click on the javascript src value. A page with the file content gets shown. It will tell you if the src does not point to an actual file available on your server.
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solved How can my html not read my js [closed]