.each()

Categories: Miscellaneous > Collection Manipulation | Traversing Chinese Translation: .each()

.each( function )Returns: jQuery

Description: Iterate over a jQuery object, executing a function for each matched element.

The .each() method is designed to make DOM looping constructs concise and less error-prone. When called it iterates over the DOM elements that are part of the jQuery object. Each time the callback runs, it is passed the current loop iteration, beginning from 0. More importantly, the callback is fired in the context of the current DOM element, so the keyword this refers to the element.

Suppose you have a simple unordered list on the page:

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<ul>
  <li>foo</li>
  <li>bar</li>
</ul>

You can select the list items and iterate across them:

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$( "li" ).each(function( index ) {
  console.log( index + ": " + $( this ).text() );
});

A message is thus logged for each item in the list:

0: foo
1: bar

You can stop the loop from within the callback function by returning false.

Note: most jQuery methods that return a jQuery object also loop through the set of elements in the jQuery collection — a process known as implicit iteration. When this occurs, it is often unnecessary to explicitly iterate with the .each() method:

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// The .each() method is unnecessary here:
$( "li" ).each(function() {
  $( this ).addClass( "foo" );
});
 
// Instead, you should rely on implicit iteration:
$( "li" ).addClass( "bar" );

Examples:

Iterate over three divs and sets their color property.

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<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>each demo</title>
  <style>
  div {
    color: red;
    text-align: center;
    cursor: pointer;
    font-weight: bolder;
    width: 300px;
  }
  </style>
  <script src="https://code.jquery.com/jquery-1.10.2.js"></script>
</head>
<body>
 
<div>Click here</div>
<div>to iterate through</div>
<div>these divs.</div>
 
<script>
$( document.body ).click(function() {
  $( "div" ).each(function( i ) {
    if ( this.style.color !== "blue" ) {
      this.style.color = "blue";
    } else {
      this.style.color = "";
    }
  });
});
</script>
 
</body>
</html>

Demo:

To access a jQuery object instead of the regular DOM element, use $( this ). For example:

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<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>each demo</title>
  <style>
  ul {
    font-size: 18px;
    margin: 0;
  }
  span {
    color: blue;
    text-decoration: underline;
    cursor: pointer;
  }
  .example {
    font-style: italic;
  }
  </style>
  <script src="https://code.jquery.com/jquery-1.10.2.js"></script>
</head>
<body>
 
To do list: <span>(click here to change)</span>
<ul>
  <li>Eat</li>
  <li>Sleep</li>
  <li>Be merry</li>
</ul>
 
<script>
$( "span" ).click(function() {
  $( "li" ).each(function() {
    $( this ).toggleClass( "example" );
  });
});
</script>
 
</body>
</html>

Demo:

Use return false to break out of each() loops early.

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<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>each demo</title>
  <style>
  div {
    width: 40px;
    height: 40px;
    margin: 5px;
    float: left;
    border: 2px blue solid;
    text-align: center;
  }
  span {
    color: red;
  }
  </style>
  <script src="https://code.jquery.com/jquery-1.10.2.js"></script>
</head>
<body>
 
<button>Change colors</button>
<span></span>
<div></div>
<div></div>
<div></div>
<div></div>
<div id="stop">Stop here</div>
<div></div>
<div></div>
<div></div>
 
<script>
$( "button" ).click(function() {
  $( "div" ).each(function( index, element ) {
    // element == this
    $( element ).css( "backgroundColor", "yellow" );
    if ( $( this ).is( "#stop" ) ) {
      $( "span" ).text( "Stopped at div index #" + index );
      return false;
    }
  });
});
</script>
 
</body>
</html>

Demo: