title: Data structure to store unique values in javascript
body: <p>What is the best data type to store unique values only?
  an array can have duplicates</p>
  
  <pre><code>[one, one, two]
  </code></pre>
  
  <p>and an object (? maybe wrong terminology) have unnecessary values for my current case</p>
  
  <pre><code>{one: something, two: something, three: something}
  </code></pre>
  
  <p>Shortly, I need something like this:</p>
  
  <pre><code>{one, two, three}
  </code></pre>
  
  <p>I am not sure what it is called, or if it does exist in js. Needing some enlightment.</p>