JavaScript calculate distance between 2 points

gistfile1.js

function toRad(value) {
	  var RADIANT_CONSTANT = 0.0174532925199433;
	  return (value * RADIANT_CONSTANT);
	}

	function calculateDistance(starting, ending) {
	  var KM_RATIO = 6371;
	  try {      
	    var dLat = toRad(ending.latitude - starting.latitude);
	    var dLon = toRad(ending.longitude - starting.longitude);
	    var lat1Rad = toRad(starting.latitude);
	    var lat2Rad = toRad(ending.latitude);
	    
	    var a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
	            Math.sin(dLon / 2) * Math.sin(dLon / 2) * Math.cos(lat1Rad) * Math.cos(lat2Rad);
	    var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
	    var d = KM_RATIO * c;
	    return d;
	  } catch(e) {
	    return -1;
	  }
	}