ajax find,.find()

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; all parts of the selector must lie inside of an element on which .find() is called. 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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• I
• II
  • A
  • B
    • 1
    • 2
    • 3
  • C
• III

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.