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Using the jQuery .each() Function

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Using the jQuery .each() Function

With jQuery dominating JavaScript development, this article is a deep dive into one of the main functions in the library— each().

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In this article, we're going to look into the usage of the jQuery each() function which will allow us to loop through different datasets such as arrays or objects. jQuery each is one of the most used functions in jQuery so I think it's important to understand what you can do with it.

The jQuery each function is used to loop through data the easiest way to think of it is that it's similar to a foreach loop in other languages. So, you can use it to loop through a number of DOM objects from the same selectors. For example, if you want to add a target="_blank" to all links on the page then you will select all links and loop through each of them to add a target="_blank".

$('a').each(function(i){
    $(this).attr('target', '_blank');
});

Let's investigate how this works. First, we get all the anchor links on the page by using the following selector.

// Get all anchor links
$('a')

Next, we use the each function to loop through all the links.

$('a').each(function(i){
    // Performs tasks to each of the links
});

When you're inside the each function you can access the current element it is loop through by using the this keyword, but this object will not be a jQuery object and therefore if it's a DOM element you will not be able to use any jQuery functions on it. The solution to this problem is to wrap the this inside a jQuery object definer.

$('a').each(function(i){
    // Performs tasks to each of the links
    $(this);
});

When we have the current looped element inside a jQuery object we can then add a new attribute to the link by using the attr function.

$('a').each(function(i){
    $(this).attr('target', '_blank');
});

Get the Current Index of the Loop

In the above example, you'll notice the i inside the function() parameters. This variable is populated with the current index of the each to see this working have 10 links on the page.

<a>Link 1</a>
<a>Link 2</a>
<a>Link 3</a>
<a>Link 4</a>
<a>Link 5</a>
<a>Link 6</a>
<a>Link 7</a>
<a>Link 8</a>
<a>Link 9</a>
<a>Link 10</a>

Then output the current index by alerting this to the user.

$('a').each(function(i){
    alert(i);
});

Loop Through Arrays

In the above example, you saw how you can select DOM elements and loop through them but you can also use it to loop through arrays of data and get both the index and the value of the position inside the array.

var fruit = ['orange', 'apple', 'banana', 'grapes', 'kiwi'];

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

In the console, it will output the following.

"0 orange""1 apple""2 banana""3 grapes""4 kiwi"

Loop Through Objects

What if you're using objects to store data and not arrays, the each function will take care of that the same way as you can see in the following code.

var fruitObj = {
   1: 'orange',
   2: 'apple',
   3: 'banana',
   4: 'grapes',
   5: 'kiwi'
};

$.each(fruitObj, function(key, value){
  console.log(key + ' ' + value);
});

The output of looping through the object is below.

"1 orange""2 apple""3 banana""4 grapes""5 kiwi"

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Topics:
jquery ,javascript ,web dev

Published at DZone with permission of Paul Underwood, DZone MVB. See the original article here.

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