CSS is one of the essential skills for front-end developers, and CSS3 is an advanced version of CSS that includes more powerful features and functions. In CSS3, the is selector and where selector are two very practical programming optimization techniques that can help developers write style code more efficiently.
1. Introduction to the is selector
The is selector is a new selector in CSS3. It can match multiple selectors at the same time and only needs to write the same code once. For example, suppose we have a list and need to apply the same style to the li tags in it. The traditional way of writing is to select each li tag separately and set the style. The code will look very verbose:
li:nth-child(1) {
...
}
li:nth-child(2) {
...
}
li:nth- child(3) {
...
}
With the is selector, we can write the same style code together to make the code more concise and readable:
: is(li:nth-child(1), li:nth-child(2), li:nth-child(3)) {
...
}
In this way, we Not only can it improve the maintainability of style code, it can also reduce the amount of code and improve development efficiency.
2. Introducing the where selector
The where selector is also a new selector in CSS3. It has a similar function to the is selector, but the syntax is different. The syntax of the where selector is more flexible and can select elements based on different conditions. For example, we want to apply the same style when selecting elements with a certain class name or when the current element is an element of a specific type. The traditional way of writing is to use multiple selectors and set the same style:
[ class*="example"] {
...
}
[type="checkbox"] {
...
}
[type="radio" ] {
...
}
With the where selector, we can merge these selectors together to make the code more concise:
:where([class*= "example"], [type="checkbox"], [type="radio"]) {
...
}
Such code can improve the readability of the code, and when needed It is also more convenient when modifying styles.
3. Examples of skillfully using is and where selectors
The following are several examples to show how to skillfully use is and where selectors to optimize CSS programming:
:is(.btn-primary, .btn-secondary) {
border-radius: 8px;
}
This code can choose to have .btn- button with the primary or .btn-secondary class name and apply the rounded border style.
tr:nth-child(even) {
background-color: #f2f2f2;
}
:is([type= "checkbox"], [type="radio"]) tr:nth-child(even) {
background-color: #ffffff;
}
This code can select even rows of the table and select Rows of check boxes or radio buttons have different background colors.
:is(.square, .circle) {
width: 100px; height: 100px;
}
.square {
border-radius: 0;
}
.circle {
border-radius: 50%;
}
This code can select pictures with .square or .circle class names, and based on the class Apply a different border style to the name.
Through these examples, we can see how clever use of the is selector and where selector can improve the readability and maintainability of the code, reduce repeated style code, and make the code more concise and efficient.
Summary:
is selector and where selector are two powerful programming optimization techniques provided by CSS3, which can help developers write style code more efficiently. Reasonable use of these two selectors can improve the readability and maintainability of the code, reduce the amount of code, and improve development efficiency. Therefore, mastering and applying the is selector and where selector is one of the essential skills for every front-end developer.
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