Convert Sting to [x, y] coordinates in javascript

Question

<script type="text/javascript">
  var src = [40.6976, -74.2598];

  function convertToDMS(src) {
    function toDMS(n) {
      n = Math.abs(n);
      var d = Math.floor(n);
      n = n - d;
      n *= 60;
      var m = Math.floor(n);
      n = n - m;
      n *= 60;
      var s = Math.floor(n);
      return "" + d + " " + m + " " + s;
    }

    var dir0 = src[0] > 0 ? "N" : "S";
    var dir1 = src[1] > 0 ? "E" : "W";

    console.log(toDMS(src[0]) + dir0);
    console.log(toDMS(src[1]) + dir1);
  }

  convertToDMS(src);
</script>
<div id="locationdiv">[40.6976,-74.2598]</div>

Using the script above I am able to get degree, minute and second like 40°41'46.0"N+74°18'08.0"W

However if instead of using 
var src = [40.6976,-74.2598];
I use
var src = document.getElementById("locationdiv").innerHTML;

the script does not work with no error in console. How do I convert the innerHTML which comes as a string to the form [40.6976,-74.2598] which can be used.