title: How to insert a string-token before occurrence of another string-token in a string with Javascript
body: <p>I have a string like this</p>
  
  <pre><code>'I am a beautiful string ABC where sometimes ABC there ABC are weird tokens ABC'
  </code></pre>
  
  <p>I need to insert another token, let's say <code>'123'</code>, before any occurrence of the token <code>'ABC'</code> in my string.
  In other words the result I want to obtain is </p>
  
  <pre><code>'I am a beautiful string 123ABC where sometimes 123ABC there 123ABC are weird tokens 123ABC'
  </code></pre>
  
  <p>I have tried several solutions, but none looks to me elegant. Any suggestion to solve this problem would be appreciated.</p>