title: Find top level key in multidimensional object by value of second level key in javascript
body: <p>I have and multidimensional object that looks like this: </p>
  
  <pre><code>obj = {
      'someString': {
          name: 'John',
          page: 'some url',
          number: 4
      },
      'someString2': {
          name: 'Bill',
          page: 'some url',
          number: 7
      }
  }
  </code></pre>
  
  <p>How do I find the first level key (in this case "someString2") where "number" is equal to 7?</p>
  
  <p>The number is always unique and is the only thing I know beforehand.</p>