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Which JS loop is fast?

Shubham Tiwari on August 08, 2022

Hello Guys Today i will discuss which loop among "for","while" and "do-while" is faster? I am comparing only these 3 loops in this post. Let's get...
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smac89 •

Next time you want to do timings in JS, instead of manually calculating the time, just use console.time(label) and it's companion console.timeEnd(label).

See docs: developer.mozilla.org/en-US/docs/W...

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Shubham Tiwari •

Thank you i will use it

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John P. Rouillard •

Which JS interpreter are you using? Is it possible it's running a JIT optimize step as part of the first run that is reflected in the
subsequent runs?

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Shubham Tiwari •

I am using node js for running these

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John P. Rouillard •

Ok, so V8. So suspect the answer to your question:

While running the loop first time in every case the time
taken is higher compared to other 9 test case, please
mention the reason in the comment section if you know that.

is probably the JIT compiler/optimizer:

blog.logrocket.com/how-javascript-...

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Shubham Tiwari •

Thank i will read this

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Suryakant Patil •

Hey, Can you test the below For loop? I guess it will give you slightly better performance.

let i=0;
for(; i<10000000000;i++){
  count += i
}
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Shubham Tiwari •

The code is not correct can you please write it correctly

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FJones • • Edited

I'm not sure where you're struggling. The error message is quite telling, in that all that's missing is:

- let i=0;
+ let i=0, count;
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Then the snippet runs. Though my quick look over it seems to make it benchmark slower than the for-scoped version, which is a bit surprising.

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Shubham Tiwari •

Yeah got it

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Andrew Baisden •

Speed and performance really become a serious requirement when you are trying to find the best data structure for your application. Especially when it has a lot of users.

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Shubham Tiwari •

Yes it is and i performed this test because I wanted to see that all these loops are equal or have some sort of difference