title: How do I calculate the time difference between strings in Javascript
body: <p>is that I have two hours in string format and I need to calculate the difference in javascript, an example:</p>
  
  <p>a = "10:22:57"</p>
  
  <p>b = "10:30:00"</p>
  
  <p>difference = 00:07:03 ?</p>