Use Performance API if available

Performance API is more precise
https://developer.mozilla.org/en-US/docs/Web/API/Performance

http://updates.html5rocks.com/2012/08/When-milliseconds-are-not-enough-performance-now

Note: I did not switch new Date().getTime() to Date.now() because it
only works with IE>8.
But this might be interesting because Date.now() is faster than new
Date().getTime() (no object creation).

http://stackoverflow.com/questions/12517359/performance-date-now-vs-date-gettime

Author: TiTi

benchmark/benchmark.js

@@ -13,19 +13,19 @@ $(function() {
         var times = 0;
 
         for (var i = 0; i < 1000; i++) {
-            var startTime = new Date().getTime();
+            var startTime = performance ? performance.now() : new Date().getTime();
             var result = astar.search(graph, start, end);
-            var endTime = new Date().getTime();
+            var endTime = performance ? performance.now() : new Date().getTime();
             times = times + (endTime - startTime);
 
             results.push(
                 '<li>Found path with ' + result.length + ' steps.  ' +
-                'Took ' + (endTime - startTime) + ' milliseconds.</li>'
+                'Took ' + (endTime - startTime).toFixed(2) + ' milliseconds.</li>'
             );
         }
 
         $("#graph").html(graph.toString());
-        $("#summary").html('Average time: ' + (times / 1000) + 'ms');
+        $("#summary").html('Average time: ' + (times / 1000).toFixed(2) + 'ms');
         $("#results").html(results.join(''));
 
         running = false;

demo/demo.js

@@ -179,18 +179,19 @@ GraphSearch.prototype.cellClicked = function($end) {
    	var $start = this.$cells.filter("." + css.start);
    	var start = this.nodeFromElement($start);
 
-	var sTime = new Date();
+	var sTime = performance ? performance.now() : new Date().getTime();
     var path = this.search(this.graph, start, end, {
         closest: this.opts.closest
     });
-	var fTime = new Date();
+	var fTime = performance ? performance.now() : new Date().getTime();
+	var duration = (fTime-sTime).toFixed(2);
 
 	if(!path || path.length == 0)	{
-	    $("#message").text("couldn't find a path ("+(fTime-sTime)+"ms)");
+	    $("#message").text("couldn't find a path (" + duration + "ms)");
 	    this.animateNoPath();
 	}
 	else {
-	    $("#message").text("search took " + (fTime-sTime) + "ms.");
+	    $("#message").text("search took " + duration + "ms.");
     	if(this.opts.debug) {
 	    	this.drawDebugInfo(this.opts.debug);
 	    }