title: Get index by value
body: <p>I want something like this:</p>
  
  <pre><code>var onlineMobilesAnon=[];
  onlineMobilesAnon["abc1"]="test";
  console.log(onlineMobilesAnon.indexOf("test"));  //Should return "abc1"
  </code></pre>
  
  <p>How can I achive this ?</p>