JavaScript for loops

Question

In JavaScript I am aware of a number of different ways to iterate over each element in an array. At present my favorite is the array.forEach(function(entry){}) style but I know there is also the traditional for (var i = 0; i < array.length; i++) as well as for (entry in array) and JQuery's $.each() method.

My question is this: given a list of variable length eg: var arr = ['abc', 'xyz', '123', ...] what's the best way to loop over each element?

Don't use `for (entry in array)` for arrays. It's specifically for iterating over objects and you can get into trouble if you use it for arrays. — Andy, May 02 '14 at 13:17
Note that `array.forEach()` is not available in older browsers (IE8 and below, Firefox before 1.5) — Paul Roub, May 02 '14 at 13:17
With jQuery you obviously have the added overhead of adding in jQuery. I prefer a tradition `for-loop`. — Andy, May 02 '14 at 13:18
[relevant reading](http://stackoverflow.com/q/9329446/497418) — zzzzBov, May 02 '14 at 13:18
nobody remembers of `while`? cause the for is based on `while` and `foreach` on `for`....so instead to do 2-3 operations you can do just 1 and buy some extra performance — HellBaby, May 02 '14 at 13:19
Check out [this link](http://www.sebarmeli.com/blog/2010/12/06/best-way-to-loop-through-an-array-in-javascript/). Very informative — Dumisani, May 02 '14 at 13:20
by my experience , the best is : for (var i = 0; i < 5; i++) because you write your functions and if some day you want to merge or rewrite your functions in another language like java, C++ or php you 'll have just a little changes. unlike jquery has his own language. — Mimouni, May 02 '14 at 13:22
Answering your new question: You can use the `for(var i=0; i<5; i++)` for read your array or `for (var i = 0; i < array.length; i++)` — Jabel Márquez, May 02 '14 at 13:46

score 4 · Accepted Answer · answered May 02 '14 at 13:17

4

For performance I would favor:

for (var i = 0; i < 5; i++)

For ease of use I generally use:

array.forEach(function(entry){})

Or for DOM elements I prefer jQuery: $.each()

answered May 02 '14 at 13:17

Patrick Hofman

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What makes for (var i = 0; i < 5; i++) better for performance? – nettux May 02 '14 at 13:49
@nettux443: When you use other objects to iterate over them, like jQuery, you will always have performance loss. `for` is just the most bare metal way of iterating. – Patrick Hofman May 02 '14 at 13:50

Jabel Márquez · Answer 2 · 2014-05-02T13:28:03.460

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Is not better one than other.

The for each loops are when you don't know how many items are in the array. array.forEach(function(entry){}) or $.each()

The basic loop (for) is when you know the especific number of items in the array. for (var i = 0; i < 5; i++). And this is less load for the process.

edited May 02 '14 at 13:28

answered May 02 '14 at 13:19

Jabel Márquez

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you can say for (var i = 0; i < array.length; i++). foreach is great if you don't have an easy way to know how many items are in a collection. – Nzall May 02 '14 at 13:32

score 0 · Answer 3 · answered May 02 '14 at 13:16

for (entry in array) is the one that is the most different in that it is a way to iterate over properties of an object, and not items in a list. It's not like a traditional foreach

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...in

JavaScript for loops

3 Answers3