title: Faster to access numeric property by string or integer?
body: <p>In JavaScript you can get and set indexes of arrays and "numeric" properties of objects using either an integer or a string and get the same results:</p>
  
  <pre><code>var a=[], o={};
  a[1]    = "foo";  a["1"]   == "foo" // true
  a["2"]  = "bar";  a[2]     == "bar" // true
  a["-3"] = "baz";  a[-.3e1] == "baz" // true
  o[1]    = "foo";  o["1"]   == "foo" // true
  o["2"]  = "bar";  o[2]     == "bar" // true
  o["-3"] = "baz";  o[-.3e1] == "baz" // true
  </code></pre>
  
  <p>While strings and numbers are interopable&mdash;for both getting and setting&mdash;which is faster (for both arrays and for objects)?</p>