A Deep Dive into jQuery Filters: Explore what elements are included in the filter functionality

jQuery is a very popular JavaScript library used to simplify DOM manipulation and event handling. In jQuery, filters are a powerful feature that help developers select specific elements or a group of elements. This article will provide an in-depth analysis of jQuery filters, detailing different types of filters and how to use them, along with code examples to help readers better understand and use this feature.

1. Basic filter

1.1 :first

##:first filter is used to select the first matching element . For example, the following code will select the first

element:

$("div:first")

1.2

:last

##:last

Filter is used to select the last matching element. The sample code is as follows: <pre class='brush:javascript;toolbar:false;'>$(&quot;div:last&quot;)</pre>1.3

:even

and :odd

:even

The filter selects elements at even positions , while the :odd filter selects elements at odd positions. The sample code is as follows: <pre class='brush:javascript;toolbar:false;'>$(&quot;ul li:even&quot;) // 选择&lt;ul&gt;下偶数位置的&lt;li&gt;元素 $(&quot;ul li:odd&quot;) // 选择&lt;ul&gt;下奇数位置的&lt;li&gt;元素</pre>2. Content filter

2.1

:contains()

:contains()

Filtering The selector selects elements containing the specified text. The sample code is as follows: <pre class='brush:javascript;toolbar:false;'>$(&quot;p:contains('Hello')&quot;) // 选择包含文本“Hello”的&lt;p&gt;元素</pre>2.2

:empty

and :parent

:empty

filters select those without child elements element, while the :parent filter selects elements that have at least one child element. The sample code is as follows: <pre class='brush:javascript;toolbar:false;'>$(&quot;div:empty&quot;) // 选择空的&lt;div&gt;元素 $(&quot;div:parent&quot;) // 选择有子元素的&lt;div&gt;元素</pre>3. Visibility filter

3.1

:visible

and :hidden

The :visible

filter selects visible elements, while the :hidden filter selects hidden elements. The sample code is as follows: <pre class='brush:javascript;toolbar:false;'>$(&quot;.menu:visible&quot;) // 选择可见的菜单元素 $(&quot;form:hidden&quot;) // 选择隐藏的表单元素</pre>4. Form filter

4.1

:input

:input

Filter selects all Input elements, including input, select, textarea, etc. The sample code is as follows: <pre class='brush:javascript;toolbar:false;'>$(&quot;form :input&quot;) // 选择表单中的所有输入元素</pre>4.2

:checked

and :selected

:checked

The filter selects the selected complex Select box or radio button, :selectedFilter selects the selected <option></option> element. The sample code is as follows: <pre class='brush:javascript;toolbar:false;'>$(&quot;input:checked&quot;) // 选择被选中的输入框 $(&quot;option:selected&quot;) // 选择被选中的&lt;option&gt;元素</pre>5. Custom filters

In addition to the built-in filters, you can also write custom filters. The following is an example:

$.expr[':'].startsWith = function (element, index, match) {
    return $(element).text().trim().startsWith(match[3]);
};

$("ul li:startsWith('A')")  // 选择以“A”开头的<li>元素

Conclusion

Through the introduction of this article, readers have a deeper understanding of jQuery filters. Filters can help developers accurately select elements that need to be operated and improve code efficiency and readability. In actual development, it is very important to choose appropriate filters based on project requirements. Custom filters can also be written according to needs to meet specific needs. I hope this article can help readers better master the use of jQuery filters and improve their front-end development skills.

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