How to manage my Project?

I’m learning coding and i’mworking on a project on Sublime Text and i have an html code and a js code, i used to put my js code in the html code by using the script tag but this not efficient and readable, but i know there is a different way by using You can see it below:
But this way dosen’t work.
Can you help me to fix it?

I’m not sure what you mean by

when you view the page in the browser does the script not load? is something in the script not working?

Generally, the best place to put your script tags is the last thing in your body tag since the browser will load things top to bottom.

<!doctype html>
  <!-- meta and css, the meta below helps with phones displaying currectly -->
  <meta name="viewport" content="width=device-width, initial-scale=1">

  <title>just taking the control</title>

  <!-- Aditinal html -->

  <!-- script tags -->
  <script type="text/javascript" src="sandbox.js"></script>

Yeah the javascript code dosen’t run actually

Was the javascript file in the same directory as your html?

Yeah! It was, does that change anything?

No it should’t change anything, if you open up your browsers console control+shift+j in Chrome do you see any errors, is there anything in the javascript?