The principle of scoped in vue

The scoped attribute in Vue limits CSS styles to components by appending unique class names to avoid accidental interference. It uses a Sass/Less preprocessor to convert scoped styles into CSS with unique class names, enabling CSS style isolation, reusability, and clarity. But it may slightly reduce performance, and the style can only be applied to elements within the component. It is recommended to use scoped when a component has a unique visual style, needs to prevent style conflicts, or creates reusable components.

The principle of scoped in Vue

Overview
scoped is one of the methods in Vue Property used to limit the scope of CSS styles to specific components. This prevents CSS styles from other components from accidentally affecting this component.

Principle
Scoped works by appending a unique class name to the root element of each component that uses the scoped attribute. This class name is generated by Vue and is used to isolate a component's CSS styles from those of other components.

When the component's template is parsed, Vue will add the component's scoped style block to a global CSS style sheet. However, these styles are used with the component's unique class name, which ensures that they only apply to that component and its descendant elements.

Specific implementation
Vue uses Sass/Less preprocessor to implement scoped. During the compilation phase, Vue will automatically convert the component's scoped style blocks into CSS styles with unique class names. For example, if the template of a component is as follows:

<code class="html"><template scoped>
  <span>Hello World</span>
</template></code>

The compiled CSS style is as follows:

<code class="css">.unique-class-name span {
  color: red;
}</code>

Advantages
Using scoped has the following advantages:

• CSS style isolation: Prevent accidental CSS style interference.
• Reusability: Allows the creation of reusable components without worrying about style conflicts.
• Clarity: Make CSS code easier to maintain and understand.

Limitations
scoped also has some limitations:

• Performance: Due to the extra class name, scoped This may result in a slight slowdown in page loading speed.
• Restrictions: Scoped styles can only be applied to components and their descendant elements, and cannot be applied to elements outside the component.

Best Practices
It is recommended to use scoped in the following situations:

• When the component has its own unique visual style.
• When you need to prevent CSS style conflicts.
• When you want to create reusable components.

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