title: What is this : sign after a variable JS syntax?
body: <p>I came across the following valid syntax in JS when looking at <code>svelte</code> library:</p>
  
  <pre><code>$: doubled = 6 * 2;
  </code></pre>
  
  <p>At first, I thought it was specific for the library, <strong>but it works on the Chrome console</strong>. What is this syntax?</p>
  
  <p>It can be anything:</p>
  
  <pre><code>name: something = 6 * 2;
  </code></pre>