EDIT:
For hosting the JS source file on some external server for testing you can use sites like http://yourjavascript.com
You can search for more alternatives on Google but this one worked well for me :)
Original Answer:
As others pointed out in comments, you can simply put the source url of JavaScript program in src attribute of <script>
tag...
<html>
<head>
<script src="https://usscript1.000webhostapp.com/example1.js"></script>
</head>
<body>...your website's body here...</body>
</html>
Regarding the blocking issue, make sure your src link to the JavaScript file is correct (by opening the link in seperate browser tab or have look at the console in inspect page window for any errors).
You can put the script on the same site and link to it as,
<html>
<head>
<script src="/example1.js"></script>
</head>
<body>...your website's body here...</body>
</html>
If you are facing issues with putting the file on your site, you can directly put the code of JavaScript program inside <script>
tag like this...
<html>
<head>
<script>
...your JS program goes here...
</script>
</head>
<body>...your website's body here...</body>
</html>