Detailed explanation of the difference and usage of is and where selectors

Detailed explanation of the difference and usage of is and where selectors

When writing CSS style rules, we often need to select specific elements for style setting based on some conditions . CSS provides a variety of selectors to meet this need, the most commonly used of which are the is selector and the where selector. This article will introduce in detail the difference and usage of these two selectors.

First, let’s look at the is selector. The is selector can be understood as a conditional selector, which allows us to select specific elements based on their type and attributes. Its basic syntax is as follows:

.is(selector-list) {
/ Style rules/
}

is selector-list of selector The parameter is a list of selectors, which can be separated by commas. Each selector can be an element type selector, a class selector, an attribute selector, etc. Here is a code example:

In the above code, we define an is selector, which selects elements corresponding to the .box class and #paragraph id, and adds their The background color is set to red.

Corresponding to the is selector is the where selector. The role of the where selector is to select specific elements based on the hierarchical relationship of the elements. Its syntax is as follows:

selector-list where(selector) {
/ Style rules/
}

where selector’s selector-list and The selector parameters are all selectors. The selector-list is used to select the elements to be limited, and the subsequent selector is used to select the elements to which the style is ultimately applied. Here is an example:

In the above code, we use the where selector to select elements containing the .box class and set their background color to blue.

There are some differences in the use of is selector and where selector. First of all, the is selector is a selector based on element type and attributes, while the where selector is a selector based on the hierarchical relationship of elements. Secondly, the is selector can select multiple elements, while the where selector can only select one element. In addition, the is selector can only be used in a selector list, while the where selector can be used directly in style rules.

It should be noted that the is selector and where selector are currently in the experimental stage and may not be supported by all browsers. To ensure compatibility, we can use the traditional form of CSS selectors to achieve the same effect.

To summarize, the is selector and the where selector are two selectors in CSS that are used to conditionally select elements and apply styles. Understanding their differences and usage will help us better write flexible and maintainable CSS style rules.

I hope the introduction in this article can help readers better master the use of is selector and where selector. By flexibly using these two selectors, we can more easily implement style settings for specific elements.

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