How do you performance test JavaScript code?

Question

CPU Cycles, Memory Usage, Execution Time, etc.?

Added: Is there a quantitative way of testing performance in JavaScript besides just perception of how fast the code

Answer 1

We can always measure time taken by any function by simple date object.

var start = +new Date();  // log start timestamp
function1();
var end =  +new Date();  // log end timestamp
var diff = end - start;