Why Does Vue.js Use a Virtual DOM Instead of Direct DOM Manipulation?

Vue.js uses virtual DOM instead of directly operating DOM, in order to improve performance and development efficiency. 1) Virtual DOM is calculated through diff algorithm to minimize DOM operations and improve performance. 2) Simplify development so developers do not need to deal with DOM complexity. 3) Component reuse and combination are more efficient. The working principle of virtual DOM is to generate a comparison between the new tree and the old tree, update only the difference part, and reduce the number of DOM operations.

The reason why Vue.js uses virtual DOM instead of directly operating DOM is actually based on performance optimization and development efficiency considerations. Virtual DOM provides an efficient update mechanism that allows Vue.js to build a lightweight DOM tree in memory and then calculate the minimized actual DOM operation through the diff algorithm. This approach not only improves performance, but also simplifies the development process, as developers do not need to deal directly with the complexity and compatibility issues of DOM operations.

When I first came into contact with Vue.js, I felt both novel and confused about the concept of virtual DOM. Why not operate the DOM directly? After all, DOM operations are familiar to us. However, after in-depth research and practice, I found that the advantage of virtual DOM is that it solves the performance bottlenecks and development complexity brought about by direct DOM operations.

In Vue.js, virtual DOM works like this: When the state of the component changes, Vue generates a new virtual DOM tree, and then compares this new tree with the previous virtual DOM tree. This comparison process is called the diff algorithm, which finds the difference between the two trees. Only these differences are applied to the actual DOM, rather than re-rendering the entire page. This approach significantly reduces the number of DOM operations, thereby improving the performance of the application.

Let's look at a simple example of how a virtual DOM works:

 const vnode = {
  tag: 'div',
  props: {
    class: 'container'
  },
  children: [
    {
      tag: 'p',
      children: ['Hello, Vue.js!']
    }
  ]
};

In this example, vnode represents a virtual DOM node that describes a div element containing a paragraph. When the state changes, Vue.js will generate a new virtual DOM tree, then use the diff algorithm to find the changes and update only the necessary parts.

Another benefit of using virtual DOM is that it makes reuse and combination of components easier and more efficient. Vue.js' component system relies on virtual DOM, allowing developers to easily create and manage complex UI structures without worrying about underlying DOM operations.

However, virtual DOM is not omnipotent. In some cases, it may be more efficient to operate the DOM directly, especially if you need to do very frequent DOM operations. For example, in some games or high-performance animations, it may be more appropriate to operate the DOM directly, because the diff algorithm of the virtual DOM itself also takes time.

In actual development, I found that the following points should be paid attention to when using virtual DOM:

• Performance Optimization : Although the virtual DOM itself is already very efficient, sometimes we need to optimize further. For example, control the display and hiding of elements by using v-if and v-show instead of directly manipulating the DOM.
• Avoid unnecessary re-rendering : Reduce unnecessary rerendering by using v-once directive or computed attribute.
• Understanding the diff algorithm : Understanding the working principle of the diff algorithm can help us better design components and avoid unnecessary performance overhead.

In general, Vue.js uses virtual DOM instead of directly manipulating DOM to find a balance between performance and development efficiency. Virtual DOM not only improves the performance of the application, but also simplifies the development process, allowing us to focus more on the implementation of business logic rather than be bothered by the details of DOM operations.

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