How to write jquery level selection

With the continuous development and updating of Web front-end technology, jQuery has become the first choice of many front-end developers because jQuery is very powerful and easy to use, and can easily handle many common Web development tasks, one of which is hierarchical selection. . In this article, we will introduce how to use jQuery’s hierarchical selectors.

Hierarchical selectors allow us to select specific nodes in the DOM tree, such as selecting child elements or parent elements of a specific element. A hierarchical selector consists of selectors separated by a space character (' '), each of which restricts the selection to a selection set. For example, "div p" will select all P elements within a Div element. The following table lists some commonly used hierarchical selectors:

Table 1: Commonly used hierarchical selectors in jQuery

Selector description

Selector 1 > Selector 2 Selector 2 is the direct child element of selector 1

Selector 1 Selector 2 Selector 2 is the descendant element of selector 1

Selector 1 Selector 2 Selector 2 is The next sibling element of selector 1

Selector 1 ~ Selector 2 Selector 2 is all sibling elements after selector 1

After understanding the above selectors, we can Try building some hierarchical selectors to select nodes in the DOM tree. In the next example, we will select the direct parent of all list item (li) elements:

$( "li" ).parent();

Here, we have used the parent() method to select the direct parent of each list item. Next, we can further select the next sibling element of each parent element:

$( "li" ).parent().next();

Here, we use the next() method to select the next sibling element of the direct parent of each list item . You can also use the prev() method to select the previous element instead of the next() method to select the next element.

In addition to direct parent and sibling elements, we can also select child elements or descendant elements. In the next example, we will select all paragraph (p) elements within all elements with class "wrapper":

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

Here, we have used a space to separate the elements containing class "wrapper" and Paragraph element. We can also use the ">" selector to select direct child elements, as shown in the following example:

$( ".wrapper > p" ).css( "background-color", "yellow" );

Here, we have used the ">" selector to select the paragraph directly contained in the class "wrapper" element. Now that we have a better understanding of hierarchical selectors, we can better apply them in our own code.

Summary:

In this article, we introduced jQuery’s hierarchical selector and provided some sample code to help readers understand. Hierarchical selectors allow us to select specific nodes in the DOM tree, such as selecting child elements or parent elements of a specific element. Understanding these selectors can help you better understand jQuery operations.

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