title: Using .toSource with javascript arrays
body: <p>Here is the JavaScript I have</p>
  
  <pre><code>var testArr = [];
  testArr["foo"] = "bar";
  console.log(testArr.toSource());
  //console.log(testArr["foo"]); //logs "bar"
  </code></pre>
  
  <p>the output I get is <code>[]</code>, which is not what I was expecting. Can someone give an explanation of what is going on here?</p>