title: Javascript — two instances of the same elements
body: <p>I'm trying to write a loan calculator in Javascript. </p>
  
  <p>You can have a look here:  <a href="http://codepen.io/saltcod/pen/vHrfc" rel="nofollow">http://codepen.io/saltcod/pen/vHrfc</a></p>
  
  <p>Things are working nicely, except when I click try and add a second instance of the calculator to the page (via the + button). When I do that, the two calculators don't work independently.</p>
  
  <p>How can I make all of the calculators on a page act independently? </p>
  
  <p>Thanks for anyone able to point me in the right direction.</p>
  
  <p>Terry</p>