Detailed explanation of jQuery filtering function: discover which filters are included

jQuery is a commonly used Javascript library in front-end development. It provides rich functions to facilitate developers to operate DOM and control page elements. One of the commonly used features is filters, which help developers select page elements based on specific criteria. This article will explore jQuery's filtering capabilities in detail, including commonly used filter types and specific code examples.

Basic selectors

jQuery provides some basic selectors for selecting elements on the page, such as:

• ID selector: through the element's To select elements through the id attribute, use the # symbol;

$("#elementId")

• Class selector: To select elements through the element’s class attribute, use . Symbol;

$(".className")

• Element selector: Select elements by element tag name;

$("div")

Hierarchical selector

In addition to the basic selector , jQuery also provides many hierarchical selectors, which can select elements based on the hierarchical relationship between elements, such as:

• Child element selector: select the direct child elements of an element;

$("ul > li")

• Descendant element selector: selects all descendant elements within an element;

$("div span")

Filter

jQuery provides a rich set of filters , you can filter elements according to different conditions, such as:

• :first: select the first element;

$("li:first")

• :last: Select the last element;

$("li:last")

• :even and :odd: Select the even or odd position Element;

$("li:even")
$("li:odd")

• :eq: Selects the element at a specific position;

$("li:eq(2)")

Content filter

except In addition to basic filters, jQuery also provides some filters that filter based on element content, such as:

• :contains(): Select elements that contain specified text content ;

$("p:contains('Hello')")

• :empty: Select elements that have no child elements or no text content;

$("div:empty")

Visibility filter

jQuery also provides some filters based on element visibility, such as:

• :visible: select visible elements;

$("div:visible")

• :hidden: Select hidden elements;

$("div:hidden")

Form filter

JQuery provides specific filtering for form elements To help developers filter form elements, such as:

• :input: select all input elements (input, textarea, select and button);

$(":input")

• :checked: Select the checked check box or radio button;

$(":checked")

Custom filter

In addition to the built-in In addition to filters, developers can also customize filters to meet specific filtering needs, such as:

$.extend($.expr[':'], {
  over18: function (elem) {
    return $(elem).data("age") > 18;
  }
});

Use custom filters:

$("div:over18")

Summary

This article explores jQuery's filtering capabilities, including basic selectors, hierarchical selectors, filters, content filters, visibility filters, form filters, and custom filters. By flexibly using these filters, developers can easily select elements on the page and implement various complex operations and effects. I hope this article can help readers better understand the filtering function of jQuery and be able to use it flexibly in actual project development.

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