A detailed explanation of css nesting writing method

CSS is an important technology in front-end development, used to control the style and layout of web pages. Among them, nested writing is a commonly used CSS writing method, which can make the code more concise and easier to maintain. This article will introduce the basic rules, advantages and application scenarios of CSS nested writing to help readers better understand and use CSS.

1. Basic rules of CSS nested writing

CSS nested writing refers to defining the style of the child element in the style of the parent element, and using indentation to indicate the hierarchical relationship. For example, the following is an example of nested writing:

/* 父元素样式 */
.parent {
  background-color: #ccc;
  padding: 20px;
  /* 子元素样式 */
  .child {
    color: #333;
    font-size: 16px;
  }
}

In the above example, the style of the .child element is defined in the style of the .parent element in the block. This way of writing makes the code more readable and easier to maintain.

There are some basic rules for nested writing:

1. Child element styles must be placed within the parent element style block. Do not define child element styles within another parent element style block.

2. Multiple sub-element styles can be nested. For example:

.parent {
  /* 子元素1 */
  .child1 {
    /* 子元素2 */
    .child2 {
      /* 子元素3 */
      .child3 {
        color: #333;
      }
    }
  }
}

3. The selector of the nested style must be the child element selector of the parent element (separated by spaces). For example, .parent .child means .child is a child element of the .parent element, while .child .sub-child means .sub-child is a child element of the .child element.

2. Advantages of CSS nested writing

CSS nested writing has the following advantages:

1. Concise code: By nesting sub-element styles, duplicates can be omitted Selectors make code more concise. This helps improve code readability and maintainability.

2. Clear hierarchy: Use indentation to indicate hierarchical relationships to make the hierarchical structure of the code clearer.

3. Easy maintenance: When you need to modify the style of an element, you only need to change the style of the parent element and the style of the child element will be automatically updated at the same time.

4. High readability: Using nested writing can make it easier to understand the hierarchical relationship between elements, which helps developers quickly determine the applicable scope of styles.

3. Application scenarios of CSS nesting writing method

CSS nesting writing method is suitable for the following scenarios:

1. Nesting similar elements: When the parent element and the child element When the styles between the two are similar, you can use nested writing to make the code clearer. For example:

/* 父元素样式 */
.parent {
  background-color: #ccc;
  padding: 20px;
  /* 子元素样式 */
  .child {
    margin-bottom: 10px;
    /* 子元素内部 */
    .child-inner {
      color: #333;
      font-size: 16px;
    }
  }
}

2. Nested state changes: When an element has multiple states, nested writing can be used to express these states. For example:

/* 父元素样式 */
.parent {
  background-color: #ccc;
  padding: 20px;
  /* 子元素样式 */
  .child {
    margin-bottom: 10px;
    /* 子元素默认状态 */
    &.default {
      color: #333;
      font-size: 16px;
    }
    /* 子元素悬停状态 */
    &.hover {
      color: #fff;
      background-color: #333;
    }
  }
}

In the above example, the .child element has two states: default state and hover state. These states are defined in the style block of the .parent element, making the code easier to maintain.

4. Summary

CSS nested writing method is a commonly used CSS writing method in front-end development. It can make the code more concise, easier to read and maintain, and is suitable for scenarios where similar elements are nested and state changes are nested. In actual development, we should choose to use CSS nested writing method according to the specific situation to improve the efficiency and maintainability of the code.

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