Several selectors in css

CSS (Cascading Style Sheets) is a style language used to control the style and layout of HTML and XML files. In CSS, a selector refers to a pattern used to select HTML elements. Selectors are one of the most basic components of CSS, which can apply different styles to different elements to beautify and optimize web pages.

There are many types of selectors in CSS, each with different functions and application scenarios. In this article, we will introduce several common selectors of CSS to help readers better master the basics of CSS.

1. Tag selector

Tag selector refers to selecting the name of the HTML element as the selector. For example, to select all paragraphs, we can use p as the selector:

p {
  color: red;
  font-size: 16px;
}

The above code sets the font color of all paragraphs to red and the font size to 16 pixels. Tag selectors are great for situations where you need to apply the same style to all elements of the same type in a web page.

2. Class selector

Class selector refers to using a dot (.) as a prefix, followed by the specified class name as the selector, for example:

.button {
  background-color: blue;
  color: white;
  padding: 5px 10px;
  border-radius: 5px;
}

The above code sets the background color of all elements with class "button" to blue, the font color to white, and the border rounded corners. Class selectors are often used to specify a group of elements with a common style.

3. ID selector

The ID selector uses a # as a prefix, followed by the specified ID name as the selector, for example:

#header {
  background-color: gray;
  color: white;
  height: 100px;
}

The above code sets the background color of the element with the ID "header" to gray, the font color to white, and the height of the element to 100 pixels. The ID selector can only be used to specify a specific element because the ID of each element in HTML is unique.

4. Attribute selector

Attribute selector refers to using the attribute name and attribute value enclosed in square brackets as the selector, for example:

a[href="https://www.google.com"] {
  color: blue;
  text-decoration: none;
}

The above code sets the color of all hyperlink elements with the href attribute "https://www.google.com" to blue and removes the underline. Attribute selectors can be used to select elements more precisely and to define styles based on the element's attribute values.

5. Descendant selector

Descendant selector refers to a selector that selects by specifying the hierarchical relationship between elements. For example, if we want to select the p element within a div element, we can use the following code:

div p {
  font-style: italic;
}

The above code will set all p elements within the div element to italics. Descendant selectors can also be used to select specific elements within nested structures.

6. Child selector

The child selector refers to the selector that selects all direct child elements that meet the conditions, that is, the format of "parent element > child element". For example, if we want to select the direct child element ul in all div elements with class "menu", we can use the following code:

div.menu > ul {
  padding-left: 0;
}

The above code will select all div elements with class "menu" The left margin (padding-left) of the direct child element ul is set to 0. Child selectors have similar functionality to descendant selectors, but only work on direct child elements.

The above are several common selectors in CSS. Different selectors can select and apply different element styles according to different needs. It is hoped that readers can better master the basic knowledge of CSS by understanding these selectors, so as to write beautiful and stable web pages.

The above is the detailed content of Several selectors in css. For more information, please follow other related articles on the PHP Chinese website!