title: Will my js script break by setting css --variables on legacy browsers?
body: <p>I want to start using css --variables. For legacy browsers, the css fallback is to declare a legacy rule first, and that's fine. But then I will manipulate them via javascript. So, is it going to break the script and throw some errors in legacy browsers? I ask because I currently can't test on legacy, so I can't see by myself.</p>
  
  <p>I mean, if I do something like this:</p>
  
  <pre><code>elem.style.setProperty('--tx', `10px`);
  </code></pre>
  
  <p>What will happen in legacy browsers? Just nothing (--tx will silently not update and the program will go on) or, throw an error and break the script?</p>