title: Associative array in javascript using a pair/tuple as multi-value key/index
body: <p>In python, I can use tuples as the key to a dictionary. What's the equivalent in javascript?</p>
  
  <pre><code>&gt;&gt;&gt; d = {}
  &gt;&gt;&gt; d[(1,2)] = 5
  &gt;&gt;&gt; d[(2,1)] = 6
  &gt;&gt;&gt; d
  {(1, 2): 5, (2, 1): 6}
  </code></pre>
  
  <hr>
  
  <p>For those who are interested, I have two arrays...</p>
  
  <p><code>positions = ...</code></p>
  
  <p><code>normals = ...</code></p>
  
  <p>I need to make a third array of position/normal pairs, but don't want to have duplicate pairs. My associative array would let me check to see if I have an existing <code>[(posIdx,normalIdx)]</code> pair to reuse or create one if I don't.</p>
  
  <p>I need some way of indexing using a two-value key. I could just use a string, but that seems a bit slower than two numbers.</p>