Comprehensive explanation of jQuery filters: discover which elements are filtered

jQuery is a popular JavaScript library that is widely used in web development. In jQuery, filter is a very commonly used function, which can help developers filter out the elements that need to be operated through selectors, thereby achieving effective control of page elements. This article will comprehensively explain jQuery's filter function, mainly introduce how to use filters to discover which elements are filtered, and give specific code examples.

1. Basic filters

1. :first filter

First introduce a commonly used filter: :first. This filter selects the first element that matches. The specific usage is as follows:

$("p:first").css("background-color", "yellow");

The above code will select all paragraph elements (

) on the page and set the background color of the first paragraph element to yellow.

2. :last filter

Contrary to :first, the :last filter is used to select the last element among the matching elements. The sample code is as follows:

$("p:last").css("color", "red");

This code will select all paragraph elements on the page and set the text color of the last paragraph element to red.

3. :even and :odd filters

:even and :odd filters are used to select elements at even and odd positions in matching elements respectively. For example:

$("tr:even").css("background-color", "#f2f2f2");
$("tr:odd").css("background-color", "#e6e6e6");

The above code will set different background colors for even and odd rows in the table.

2. Content filter

4. :contains filter

:contains filter can filter elements based on the text content contained in the element. For example:

$("p:contains('jQuery')").css("font-weight", "bold");

This code will select paragraph elements containing "jQuery" text and make their text bold.

5. :empty and :not filters

:The empty filter is used to select elements that have no child elements, while the :not filter is used to exclude matching of the specified selector Elements. For example:

$("div:empty").text("这个元素没有内容");
$("p:not(.intro)").css("color", "blue");

The first piece of code will select all

elements that have no child elements on the page, and set their text content to "This element has no content". The second piece of code will select all paragraph elements with a class other than .intro and set their text color to blue.

3. Relationship filter

6. :parent and :has filter

:parent filter is used to select elements that contain child elements, and: The has filter is used to select elements that contain elements matching the specified selector. The sample code is as follows:

$("div:parent").css("border", "1px solid black");
$("ul:has(li.active)").css("background-color", "lightgrey");

The above code will select all

elements containing child elements and add black borders to them; at the same time, it will select all

elements containing class active

elements, setting their background color to light gray.

Through the above examples, we can see the powerful function of jQuery filters in web development. By making reasonable use of various filters, developers can easily find the elements that need to be operated and process them accordingly. I hope that the introduction in this article can help readers better understand and apply jQuery's filter function and improve the efficiency of web page development.

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