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

Most browsers are now implementing high resolution timing in performance.now(). It's superior to new Date() for performance testing because it operates independently from the system clock.

Usage

var start = performance.now();

// code being timed...

var duration = performance.now() - start;

References

• https://developer.mozilla.org/en-US/docs/Web/API/Performance.now()
• http://www.w3.org/TR/hr-time/#dom-performance-now