.find()

Categories: Traversing > Tree Traversal Chinese Translation: .find()

.find( selector )Returns: jQuery

Description: Get the descendants of each element in the current set of matched elements, filtered by a selector, jQuery object, or element.

Given a jQuery object that represents a set of DOM elements, the .find() method allows us to search through the descendants of these elements in the DOM tree and construct a new jQuery object from the matching elements. The .find() and .children() methods are similar, except that the latter only travels a single level down the DOM tree.

The first signature for the .find()method accepts a selector expression of the same type that we can pass to the $() function. The elements will be filtered by testing whether they match this selector. The expressions allowed include selectors like > p which will find all the paragraphs that are children of the elements in the jQuery object.

Consider a page with a basic nested list on it:

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<ul class="level-1">
  <li class="item-i">I</li>
  <li class="item-ii">II
    <ul class="level-2">
      <li class="item-a">A</li>
      <li class="item-b">B
        <ul class="level-3">
          <li class="item-1">1</li>
          <li class="item-2">2</li>
          <li class="item-3">3</li>
        </ul>
      </li>
      <li class="item-c">C</li>
    </ul>
  </li>
  <li class="item-iii">III</li>
</ul>

If we begin at item II, we can find list items within it:

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$( "li.item-ii" ).find( "li" ).css( "background-color", "red" );

The result of this call is a red background on items A, B, 1, 2, 3, and C. Even though item II matches the selector expression, it is not included in the results; only descendants are considered candidates for the match.

Unlike most of the tree traversal methods, the selector expression is required in a call to .find(). If we need to retrieve all of the descendant elements, we can pass in the universal selector '*' to accomplish this.

Selector context is implemented with the .find() method; therefore, $( "li.item-ii" ).find( "li" ) is equivalent to $( "li", "li.item-ii" ).

As of jQuery 1.6, we can also filter the selection with a given jQuery collection or element. With the same nested list as above, if we start with:

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var allListElements = $( "li" );

And then pass this jQuery object to find:

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$( "li.item-ii" ).find( allListElements );

This will return a jQuery collection which contains only the list elements that are descendants of item II.

Similarly, an element may also be passed to find:

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var item1 = $( "li.item-1" )[ 0 ];
$( "li.item-ii" ).find( item1 ).css( "background-color", "red" );

The result of this call would be a red background on item 1.

Examples:

Starts with all paragraphs and searches for descendant span elements, same as $( "p span" )

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<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>find demo</title>
  <script src="https://code.jquery.com/jquery-1.10.2.js"></script>
</head>
<body>
 
<p><span>Hello</span>, how are you?</p>
<p>Me? I'm <span>good</span>.</p>
 
<script>
$( "p" ).find( "span" ).css( "color", "red" );
</script>
 
</body>
</html>

Demo:

A selection using a jQuery collection of all span tags. Only spans within p tags are changed to red while others are left blue.

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<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>find demo</title>
  <style>
  span {
    color: blue;
  }
  </style>
  <script src="https://code.jquery.com/jquery-1.10.2.js"></script>
</head>
<body>
 
<p><span>Hello</span>, how are you?</p>
<p>Me? I'm <span>good</span>.</p>
<div>Did you <span>eat</span> yet?</div>
 
<script>
var spans = $( "span" );
$( "p" ).find( spans ).css( "color", "red" );
</script>
 
</body>
</html>

Demo:

Add spans around each word then add a hover and italicize words with the letter t.

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<!doctype html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>find demo</title>
  <style>
  p {
    font-size: 20px;
    width: 200px;
    color: blue;
    font-weight: bold;
    margin: 0 10px;
  }
  .hilite {
    background: yellow;
  }
  </style>
  <script src="https://code.jquery.com/jquery-1.10.2.js"></script>
</head>
<body>
 
<p>
  When the day is short
  find that which matters to you
  or stop believing
</p>
 
<script>
var newText = $( "p" ).text().split( " " ).join( "</span> <span>" );
newText = "<span>" + newText + "</span>";
 
$( "p" )
  .html( newText )
  .find( "span" )
    .hover(function() {
      $( this ).addClass( "hilite" );
    }, function() {
      $( this ).removeClass( "hilite" );
    })
  .end()
  .find( ":contains('t')" )
    .css({
      "font-style": "italic",
      "font-weight": "bolder"
    });
</script>
 
</body>
</html>

Demo: