title: Why do I need jquery-migrate-1.4.1.js after a successful jQuery upgrade?
body: <p>I am done upgrading jQuery from 1.3.1 to 1.12.4. Everything is working correctly and I am ready to remove jquery-migrate-1.4.1.js because I was only using it for debugging purposes during the upgrade process.</p>
  
  <p>When I remove jquery-migrate-1.4.1.js from the <code>&lt;head&gt;</code> section of my website, the page does not work properly anymore. Something breaks in the JavaScript/jQuery. I was reading <a href="https://blog.jquery.com/2016/05/19/jquery-migrate-1-4-1-released-and-the-path-to-jquery-3-0/" rel="nofollow noreferrer">https://blog.jquery.com/2016/05/19/jquery-migrate-1-4-1-released-and-the-path-to-jquery-3-0/</a> trying to find information about it, and this is something I found:</p>
  
  <blockquote>
    <p>Remove the Migrate 1.x plugin and ensure the page still works properly without it loaded.</p>
  </blockquote>
  
  <p>Why do I need jquery-migrate-1.4.1.js after a successful jQuery upgrade? I thought it was only a "behind the scenes" script for debugging purposes exclusively, not to maintain any jQuery/JavaScript functionality.</p>