title: momentjs change string mm/yyyy format to yyyy-mm
body: <p>I have a <code>date</code> string <code>11/2004</code> that comes to me via an API and on mobile I am trying to display this on a <code>date</code> field.</p>
  
  <p>If i try to render this as it is I see the following warning on console</p>
  
  <blockquote>
    <p>The specified value "11/2004" does not conform to the required format.
    The format is "yyyy-MM" where yyyy is year in four or more digits, and
    MM is 01-12.</p>
  </blockquote>
  
  <p>so using momentjs i thought this should be easy to change to date or month format but i am struggling with it as i cant seem to get the output i want.</p>
  
  <p>I tried the following code but that give me <code>invalid date</code></p>
  
  <pre><code>moment('11/2004').format('yyyy-MM')
  </code></pre>
  
  <p>What am i doing wrong here? How do i display the date on an input field in the correct format? I cant change the field type to anything else as its a date picker field on mobile.</p>