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Asked: 2026-06-01T06:01:20+00:00

I am currently reading High Performance JavaScript by Nicholas C. Zakas and in the

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I am currently reading High Performance JavaScript by Nicholas C. Zakas and in the book he says things like:

Comparing the two pieces of code shows that using the Selectors API is
2 to 6 times faster across browsers (Figure 3-6).

Figure 3-6. The benefit of using the Selectors API instead of iterating over the results of getElementsbyTagName()

What I’m looking for is a browser based tool that lets me capture and measure the performance of a given piece of JavaScript and compare it against another script that uses a different approach (e.g., using the Selector API vs getElementsByTagName).

I’ve used Chrome and Firebug, but neither of them really seem to give me the kind of comparisons he’s doing here. Am I using these tools incorrectly or is there a new tool I’m not familiar with that I should be using?

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1 Answer

  1. Editorial Team

    The most popular approach is just use the free online services of http://jsperf.com/.

    Or clone it from github.

    It has one big advantage over manual testing: It uses a Java Applet which gives access to a nanosecond timer, while JS timers (Date objects) can only resolve to milliseconds.

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