title: Enum reverse lookup
body: <p>Suppose I have an enum:</p>
  
  <pre><code>enum Color {Red = 1, Green, Blue};
  </code></pre>
  
  <p>If I have a number, I can get the enum key by doing this:</p>
  
  <pre><code>var colorName: string = Color[2]; // colorName = "Green"
  </code></pre>
  
  <p>However, that gives me a string. How can I make it so that I get a variable of type Color instead? i.e.:</p>
  
  <pre><code>colorName : Color == Color.Green
  </code></pre>