How to optimize CSS programming using the is selector

How to use the is selector to optimize CSS programming

In front-end development, CSS is an integral part. Correct definition and use of CSS selectors is to ensure page style. One of the keys to correct and optimized code. Among them, the is selector is a powerful but rarely used selector in CSS. This article will introduce what is is selector and how to use is selector correctly to optimize CSS programming.

1. What is the is selector?
The is selector is a new selector in CSS Level 4, which is implemented by using the is keyword and brackets to wrap the selector. Its function is to select a state or pseudo-class of the specified selector. Use the is selector to visually represent an element's state or relationship to other selectors. It is worth mentioning that the is selector is defined by defining an extended selector and passing it as a parameter to the is keyword.

2. How to use the is selector
The following are some common scenarios for using the is selector:

1. Select the specified pseudo-class
   Using the is selector can be very easy Conveniently select the specified pseudo-class, such as selecting the a element in the link state:

a:is(:link) {
  color: blue;
}

2. Select the specified selector
   is selector can also select the specified selector, used Simplify the code. For example, to select an element whose class name contains "btn" and is also a tag:

a:is(.btn) {
  /* styles */
}

3. Used in combination with other selectors
   is selector can be used in combination with other selectors, Further optimize code readability. For example, select all title elements (h1-h6) that also contain elements with the class name "main":

:is(h1, h2, h3, h4, h5, h6).main {
  /* styles */
}

4. Select the specified state
   is selector can also select the specified status, such as selecting a disabled input element:

input:is(:disabled) {
  /* styles */
}

When using the is selector, you need to pay attention to the following points:

1. Browser support
   Currently , the is selector is not yet fully supported in all major browsers. It is recommended to use other CSS processing tools, such as autoprefixer, etc., when using the is selector to provide compatibility.
2. Nesting and performance
   The nesting of is selectors will increase the complexity of the selector and potentially affect performance. Therefore, use the is selector with caution and avoid multiple levels of nesting.
3. Compatibility writing method
   When the browser does not support the is selector, you can use compatibility writing method to achieve the same effect. For example, the way to select an element with both class names "btn" and "a" can be changed to:

.btn.a {
  /* styles */
}

Conclusion:
is selector is a very useful selector that can Simplify CSS programming and improve code readability. Although this selector may not be fully supported by all browsers at present, reasonable use of the is selector in your project will bring some convenience to development. By understanding the usage and precautions of the is selector, we can use selectors more flexibly in CSS programming, improving development efficiency and code quality.

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