Javascript double if statement checking conditions

I am experiencing an issue with my if statement shown below:

    heatmapData = [];
    for (var i = 0; i < ob.d.length; i++) {
               if (document.getElementById("infobox").value == "10") {
                   if (ob.d[i][3] == "21/04/2016") {
                       var c = [ob.d[i][1], ob.d[i][2]];
                       var pointLL = new google.maps.LatLng(c[0], c[1]);
                       heatmapData.push(pointLL);
                   }
               }
           }

I am relatively new to javascript and was looking for some guidance as to why this isn't working. Thanks for any help in advance.