Javascript: How to measure time taken by a function to execute

Question

I need to get time in milliseconds. Please advise.

Answer 1

Use Firebug, enable both Console and Javascript. Click Profile. Reload. Click Profile again. View the report.

Answer 2

use Date().getTime()

The getTime() method returns the number of milliseconds since midnight of January 1, 1970.

ex.

var start = new Date().getTime();

for (i = 0; i < 50000; ++i) {
// do something
}

var end = new Date().getTime();
var time = end - start;
alert('Execution time: ' + time);

alternatively, getMilliseconds() will give the milliseconds of the current Date object.

Answer 3

Be aware that the results from new Date().getTime() may not give you milliseconds precision.

Take a look at this

Answer 4

You can use console.time: (only with firebug+firefox)

console.time('someFunction timer');

function someFunction(){ ... }

console.timeEnd('someFunction timer')