Comprehensive explanation and example analysis of computer compound selector

Comprehensive analysis and examples of computer compound selectors

In front-end development, the selector is an important technology, which can accurately locate the target element and add styles or bind events to it. . In CSS, there are many types of selectors, including compound selectors. This article will provide a comprehensive analysis of computer compound selectors and provide readers with some examples to help readers better understand and apply compound selectors.

1. What is a computer compound selector?

Computer compound selector (Compound selector) refers to a selector that is composed of multiple simple selectors and is used to select items that meet compound conditions. element. By combining multiple simple selectors, compound selectors can select target elements more accurately and improve the efficiency of CSS selectors.

Common compound selectors include the following:

1. Group selector: Use commas to combine multiple selectors together, and you can select multiple ones at the same time Different elements.

Example:

h1, h2, h3 {
   color: red;
}

The above code will select all h1, h2 and h3 elements at the same time and set red color for them.

2. Descendant selector: Use spaces to combine multiple selectors to select descendant elements in the parent element.

Example:

ul li {
   color: blue;
}

The above code will select all li elements under the ul element and set blue color to them.

3. Child selector: Use the greater than sign (>) to combine parent elements and child elements, indicating that only the direct child elements of the parent element are selected.

Example:

ul > li {
   color: green;
}

The above code will select all direct child elements li of the ul element and set green color for them.

4. Adjacent sibling selector: Use the plus sign ( ) to group adjacent elements together, indicating that only the element immediately following the previous element is selected.

Example:

h1 + p {
   font-weight: bold;
}

The above code will select the p elements immediately following the h1 element and set bold for them.

5. General sibling selector: Use the tilde (~) to group together all qualifying sibling elements.

Example:

h1 ~ p {
   text-decoration: underline;
}

The above code will select all p elements immediately following the h1 element and underline them.

2. Examples of compound selectors

In order to better understand and apply compound selectors, some specific examples will be given below.

Example 1: Select all a elements under all div elements with class "container".

div.container a {
   color: red;
}

In the above code, the compound selector "div.container a" selects all a elements under all div elements with class "container" and sets red for them.

Example 2: Select the direct sub-element li element under the ul element with class "nav".

ul.nav > li {
   background-color: gray;
}

In the above code, the compound selector "ul.nav > li" selects the direct child elements li under the ul element with class "nav" and sets a gray background color for them.

Example 3: Select all p elements following the element with the id "header".

#header + p {
   font-size: 16px;
}

In the above code, the compound selector "#header p" selects all p elements after the element with the id "header" and sets the font size to 16 pixels for them.

Through the above examples, readers can better understand and apply compound selectors and improve the accuracy and efficiency of selecting target elements.

Summary:

Computer compound selector is one of the important concepts in CSS selectors. By combining multiple simple selectors together, the target element can be selected more accurately. This article comprehensively analyzes the types and usage of compound selectors, and provides some examples to help readers better understand and apply compound selectors. I hope that through the introduction of this article, readers can flexibly use compound selectors in front-end development and improve their technical level.

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