title: Find key for specific value on object in JS
body: <p>I have an object as such that has been generated by using the lodash <code>_.zipObject()</code> function. So I have 2 arrays, one of locations, one of numbers.</p>
  
  <pre><code>var locs = {'Aberdeen': 304, 'Aberystwith': 109, 'Belfast': 219, 'Birmingham': 24, 'Brighton': 147, …}
  </code></pre>
  
  <p>I need to return the key based on an input value. For example, <code>function(304)</code> would return <code>'Aberdeen'</code>.</p>
  
  <p>I've tried <code>_.findkey(locs, 304);</code> but this just returns undefined. Any other attempt I've tried always returns either undefined or -1. Not really sure where to go from here.</p>