[Update] 5 jQuery.each() Function Examples | each – NATAVIGUIDES

This is an extensive overview of the jQuery.each() function — one of jQuery’s most important and most used functions. In this article, we’ll find out why and take a look at how you can use it.

What is jQuery.each()

jQuery’s each() function is used to loop through each element of the target jQuery object — an object that contains one or more DOM elements, and exposes all jQuery functions. It’s very useful for multi-element DOM manipulation, as well as iterating over arbitrary arrays and object properties.

In addition to this function, jQuery provides a helper function with the same name that can be called without having previously selected or created any DOM elements.

jQuery.each() Syntax

Let’s see the different modes in action.

The following example selects every <div> element on a web page and outputs the index and the ID of each of them:

 
$
(
'div'
)
.
each
(
function
(
index
,
 value
)
 
{
  
console
.
log
(
`
div
${
index
}
: 
${
this
.
id
}
`
)
;
}
)
;

A possible output would be:

div0:header
div1:main
div2:footer

This version uses jQuery’s $(selector).each() function, as opposed to the utility function.

The next example shows the use of the utility function. In this case the object to loop over is given as the first argument. In this example, we’ll show how to loop over an array:

 
const
 arr 
=
 
[
  
'one'
,
  
'two'
,
  
'three'
,
  
'four'
,
  
'five'
]
;

$
.
each
(
arr
,
 
function
(
index
,
 value
)
 
{
  
console
.
log
(
value
)
;
   
  
return
 
(
value 
!==
 
'three'
)
;
}
)
;

 

In the last example, we want to demonstrate how to iterate over the properties of an object:

 
const
 obj 
=
 
{
  one
:
 
1
,
  two
:
 
2
,
  three
:
 
3
,
  four
:
 
4
,
  five
:
 
5
}
;

$
.
each
(
obj
,
 
function
(
key
,
 value
)
 
{
  
console
.
log
(
value
)
;
}
)
;

 

This all boils down to providing a proper callback. The callback’s context, this, will be equal to its second argument, which is the current value. However, since the context will always be an object, primitive values have to be wrapped:

$
.
each
(
{
 one
:
 
1
,
 two
:
 
2
 
}
 
,
 
function
(
key
,
 value
)
 
{
  
console
.
log
(
this
)
;
}
)
;

 
 

`

This means that there’s no strict equality between the value and the context.

$
.
each
(
{
 one
:
 
1
 
}
 
,
 
function
(
key
,
 value
)
 
{
  
console
.
log
(
this
 
==
 value
)
;
  
console
.
log
(
this
 
===
 value
)
;
}
)
;

 
 

`

The first argument is the current index, which is either a number (for arrays) or string (for objects).

1. Basic jQuery.each() Function Example

Let’s see how the jQuery.each() function helps us in conjunction with a jQuery object. The first example selects all the a elements in the page and outputs their href attribute:

$
(
'a'
)
.
each
(
function
(
index
,
 value
)
{
  
console
.
log
(
this
.
href
)
;
}
)
;

The second example outputs every external href on the web page (assuming the HTTP(S) protocol only):

$
(
'a'
)
.
each
(
function
(
index
,
 value
)
{
  
const
 link 
=
 
this
.
href
;

  
if
 
(
link
.
match
(
/
https?:\/\/
/
)
)
 
{
    
console
.
log
(
link
)
;
  
}
}
)
;

Let’s say we had the following links on the page:

<
a
 
href
=
"
https://www.sitepoint.com/
"
>
SitePoint
</
a
>

<
a
 
href
=
"
https://developer.mozilla.org
"
>
MDN web docs
</
a
>

<
a
 
href
=
"
http://example.com/
"
>
Example Domain
</
a
>

The second example would output:

https://www.sitepoint.com/
https://developer.mozilla.org/
http://example.com/

We should note that DOM elements from a jQuery object are in their “native” form inside the callback passed to jQuery.each(). The reason is that jQuery is in fact just a wrapper around an array of DOM elements. By using jQuery.each(), this array is iterated in the same way as an ordinary array would be. Therefore, we don’t get wrapped elements out of the box.

With reference to our second example, this means we can get an element’s href attribute by writing this.href. If we wanted to use jQuery’s attr() method, we would need to re-wrap the element like so: $(this).attr('href').

2. jQuery.each() Array Example

Let’s have another look at how an ordinary array can be handled:

const
 numbers 
=
 
[
1
,
 
2
,
 
3
,
 
4
,
 
5
]
;
$
.
each
(
numbers
,
 
function
(
index
,
 value
)
{
  
console
.
log
(
`
${
index
}
: 
${
value
}
`
)
;
}
)
;

This snippet outputs:

0
:1
1
:2
2
:3
3
:4
4
:5

Nothing special here. An array features numeric indices, so we obtain numbers starting from 0 and going up to N-1, where N is the number of elements in the array.

3. jQuery.each() JSON Example

We may have more complicated data structures, such as arrays in arrays, objects in objects, arrays in objects, or objects in arrays. Let’s see how jQuery.each() can help us in such scenarios:

const
 colors 
=
 
[
  
{
 
'red'
:
 
'#f00'
 
}
,
  
{
 
'green'
:
 
'#0f0'
 
}
,
  
{
 
'blue'
:
 
'#00f'
 
}
]
;

$
.
each
(
colors
,
 
function
(
)
 
{
  $
.
each
(
this
,
 
function
(
name
,
 value
)
 
{
    
console
.
log
(
`
${
name
}
 = 
${
value
}
`
)
;
  
}
)
;
}
)
;

This example outputs:

red 
=
  
green 
=
  
blue 
=
  

We handle the nested structure with a nested call to jQuery.each(). The outer call handles the array of the variable colors; the inner call handles the individual objects. In this example each object has only one key, but in general, any number could be tackled with this code.

4. jQuery.each() Class Example

This example shows how to loop through each element with assigned class productDescription given in the HTML below:

<
div
 
class
=
"
productDescription
"
>
Red
</
div
>

<
div
>
Pink
</
div
>

<
div
 
class
=
"
productDescription
"
>
Orange
</
div
>

<
div
 
class
=
"
generalDescription
"
>
Teal
</
div
>

<
div
 
class
=
"
productDescription
"
>
Green
</
div
>

We use the each() helper instead of the each() method on the selector.

$
.
each
(
$
(
'.productDescription'
)
,
 
function
(
index
,
 value
)
 
{
  
console
.
log
(
index 
+
 
':'
 
+
 
$
(
value
)
.
text
(
)
)
;
}
)
;

In this case, the output is:

0
:Red
1
:Orange
2
:Green

We don’t have to include index and value. These are just parameters that help determine which DOM element we’re currently iterating on. Furthermore, in this scenario we can also use the more convenient each method. We can write it like this:

$
(
'.productDescription'
)
.
each
(
function
(
)
 
{
  
console
.
log
(
$
(
this
)
.
text
(
)
)
;
}
)
;

And we’ll obtain this on the console:

Red
Orange
Green

Note that we’re wrapping the DOM element in a new jQuery instance, so that we can use jQuery’s text() method to obtain the element’s text content.

5. jQuery.each() Delay Example

In the next example, when the user clicks the element with the ID 5demo all list items will be set to orange immediately.

<
ul
 
id
=
"
5demo
"
>

  
<
li
>
One
</
li
>

  
<
li
>
Two
</
li
>

  
<
li
>
Three
</
li
>

  
<
li
>
Four
</
li
>

  
<
li
>
Five
</
li
>

</
ul
>

After an index-dependent delay (0, 200, 400, … milliseconds) we fade out the element:

$
(
'#5demo'
)
.
on
(
'click'
,
 
function
(
e
)
 
{
  
$
(
'li'
)
.
each
(
function
(
index
)
 
{
    
$
(
this
)
.
css
(
'background-color'
,
 
'orange'
)
           
.
delay
(
index 
*
 
200
)
           
.
fadeOut
(
1500
)
;
  
}
)
;

  e
.
preventDefault
(
)
;
}
)
;

Conclusion

In this post, we’ve demonstrated how to use the jQuery.each() function to iterate over DOM elements, arrays and objects. It’s a powerful and time-saving little function that developers should have in their toolkits.

And if jQuery isn’t your thing, you might want to look at using JavaScript’s native Object.keys() and Array.prototype.forEach() methods. There are also libraries like foreach which let you iterate over the key value pairs of either an array-like object or a dictionary-like object.

Remember: $.each() and $(selector).each() are two different methods defined in two different ways.

This popular article was updated in 2020 to reflect current best practices and to update the conclusion’s advice on native solutions using modern JavaScript. For more in-depth JavaScript knowledge, read our book, JavaScript: Novice to Ninja, 2nd Edition.

Value to use as this when executing callbackFn .

Function to execute on each element. It accepts between one and three arguments:

forEach() calls a provided callbackFn function once
for each element in an array in ascending index order. It is not invoked for index properties
that have been deleted or are uninitialized. (For sparse arrays, see example below.)

callbackFn is invoked with three arguments:

1. the value of the element
2. the index of the element
3. the Array object being traversed

If a thisArg parameter is provided to forEach(),
it will be used as callback’s this value. The
thisArg value ultimately observable by
callbackFn is determined according to the usual rules for
determining the this seen by a function.

The range of elements processed by forEach() is set before the first
invocation of callbackFn. Elements which are assigned to indexes
already visited, or to indexes outside the range, will not be visited by
callbackFn. If existing elements of the array are changed or
deleted, their value as passed to callbackFn will be the value at
the time forEach() visits them; elements that are deleted before being
visited are not visited. If elements that are already visited are removed (e.g. using
shift()) during the iteration, later elements
will be skipped. (See
this example, below.)

Warning: Concurrent modification of the kind described in the previous paragraph frequently leads to hard-to-understand code and is generally to be avoided (except in special cases).

forEach() executes the callbackFn function once for
each array element; unlike map() or
reduce() it always returns the value
undefined and is not chainable. The typical use case is to execute side
effects at the end of a chain.

forEach() does not mutate the array on which it is called. (However,
callbackFn may do so)

Note: There is no way to stop or break a forEach() loop other than by throwing
an exception. If you need such behavior, the forEach() method is the
wrong tool.

Early termination may be accomplished with:

• A simple for
  loop
• A for…of
  / for…in
  loops
• Array.prototype.every()
• Array.prototype.some()
• Array.prototype.find()
• Array.prototype.findIndex()

Array methods: every(),
some(), find(), and findIndex() test the
array elements with a predicate returning a truthy value to determine if further
iteration is required.

Note: forEach expects a synchronous function.

forEach does not wait for promises. Make sure you are aware of the
implications while using promises (or async functions) as forEach callback.

let
 ratings 
=
 
[
5
,
 
4
,
 
5
]
;
let
 sum 
=
 
0
;

let
 
sumFunction
 
=
 
async
 
function
 
(
a
,
 b
)
{
  
return
 a 
+
 b
}

ratings
.
forEach
(
async
 
function
(
rating
)
 
{
  sum 
=
 
await
 
sumFunction
(
sum
,
 rating
)
}
)

console
.
log
(
sum
)