Measuring JavaScript execution times [US]

var counter = "";

// Start timing now with a TAG (allow you to do more than one verification at a time)
console.time("myOppTag");

for (var i = 1; i <= 1e3; i++)
    counter += i;

// ... and stop with the same TAG (No? You kidding ?)
console.timeEnd("myOppTag");

// Just for fun
console.log("Outch: " + counter);

myOppTag: 19.913ms

var counter = "";
var myTimer = {};
// Remember when we started
myTimer.start = new Date().getTime();

for (var i = 1; i <= 1e3; i++)
    counter += i;

// Remember when we finished
myTimer.end = new Date().getTime();

// Now calculate and output the difference
myTimer.result = myTimer.end - myTimer.start;
console.log(myTimer.result +' ms');

// Just for fun
console.log("Outch: " + counter);