How to make JS for loop iterate faster

Question

How to make the for loop run fast.

 for(var i =0; i<myarray.length;i++)
 {
  var nice = myarray[i];
 }

Possible duplicate of [What's the fastest way to loop through an array in JavaScript?](https://stackoverflow.com/questions/5349425/whats-the-fastest-way-to-loop-through-an-array-in-javascript) — NullPointer, Jul 18 '18 at 02:33
Try this instead: `var nice = myarray[myarray.length - 1]`, no iteration required! — CertainPerformance, Jul 18 '18 at 02:38

score -1 · Answer 1 · answered Jul 18 '18 at 02:31

-1

The best practice is to initiate the max value:

for(var i =0; max=myarray.length;i<max;i++)
{
 // codes here
}

the reason is the length of the array is accessed on every loop iteration. This can slow down your code, especially when myarray is not an array but an HTMLCollection object.

answered Jul 18 '18 at 02:31

li bing zhao

1,388
13
12

Although JS runtimes will likely optimize this away. – Dave Newton Jul 18 '18 at 02:34
1

Yes a `SyntaxError` will definitely finish faster than a valid loop. – Patrick Roberts Jul 18 '18 at 02:39

score -1 · Answer 2 · answered Jul 18 '18 at 02:41

the mirco -optimization way is to use count down:

var i,myarray=[];
for(i=myarray.length;i--;){
}

use one less variable(no max)
Count down to 0, which is usually faster because it is more efficient to compare to 0 than the length of the array or to anything other than 0.

How to make JS for loop iterate faster

2 Answers2