CSS3 Programming Tips: Master the Magical Use of is and Where Selectors

CSS3 programming skills: Master the magical use of is and where selectors

Introduction:
In front-end development, CSS plays a very important role. It not only It can beautify the page and achieve various interactive effects. With the development of CSS3, many powerful functions have been added, among which the is selector and where selector are undoubtedly very practical tools. This article will introduce the basic usage of is and where selectors, and explore their magical uses in actual development.

1. How to use the is selector
The is selector is a new selector in CSS3, which can match multiple selectors in one selector at the same time. Usually, when we write styles, if multiple elements have the same style, we use commas to separate multiple selectors, which will lead to duplicate code. The is selector can solve this problem very well and make the code more concise.

The syntax of the is selector is as follows:

:is(selector1, selector2, ...)

Among them, selector1 and selector2 are selectors, which can be class selectors, label selectors, pseudo-class selectors, etc.

For example, suppose we have two divs with class names of "box1" and "box2". They both need to set the same style. We can write like this:

.box1,
.box2 {
  background-color: red;
  width: 100px;
  height: 100px;
}

But Using the is selector, we can write code more concisely:

:is(.box1, .box2) {
  background-color: red;
  width: 100px;
  height: 100px;
}

This way, multiple selectors can be matched at the same time, avoiding repeated code.

2. How to use the where selector
The where selector is also a new selector in CSS3. It can specify conditions in a selector sequence to determine whether the element matches the selector. sequence. The introduction of where selector can help us write selectors more flexibly and improve code reusability.

The syntax of where selector is as follows:

:where(selector1, selector2, ...) {
  /* CSS规则 */
}

Among them, selector1 and selector2 are selector sequences, which can be class selectors, label selectors, pseudo-class selectors, etc.

For example, suppose we have a div with a class name of "box", and we only want to modify its style under certain conditions. We can write like this:

.box:nth-child(odd) {
  background-color: blue;
}
.box:nth-child(even) {
  background-color: green;
}
.box:nth-child(3) {
  background-color: yellow;
}

Use where Selector, we can write code more concisely:

:where(.box:nth-child(odd),
       .box:nth-child(even),
       .box:nth-child(3)) {
  background-color: blue;
}

This way, the same styles can be stored in one place, improving the maintainability of the code. Moreover, we can also add or delete styles according to different conditions, making the code more flexible.

Summary:
is selector and where selector are two new selectors in CSS3, and they are very practical in actual development. The is selector can match multiple selectors at the same time, simplifying code writing; the where selector can determine whether an element matches the selector sequence based on conditions, improving code reusability. Mastering the use of these two selectors can make us more flexible in responding to various needs in front-end development.

I hope this article will be helpful to everyone in CSS3 programming. Let us master the magical uses of is and where selectors and improve our development efficiency!

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