How vue.js implements two-way binding

Vue.js is a popular front-end framework that enables quickly building interactive web applications and user interfaces. One of the most important features in Vue.js is two-way data binding. This article will take an in-depth look at how Vue.js implements two-way data binding and how it synchronizes with views.

1. What is two-way data binding?

Two-way binding is a data binding mechanism that has two directions: data model to view and view to Data model. It allows modifying view elements in Vue.js applications and updating related data in the data model. This real-time, two-way data synchronization can greatly simplify application logic and development workflow.

2. How does Vue.js implement two-way data binding?

Vue.js uses a technology called "data hijacking" to achieve two-way data binding. Data hijacking means that when an object property is accessed or modified, its value is intercepted and responded to. Vue.js relies on Object.defineProperty in ES5 to define a property on an object. When the property is accessed or modified, the getter and setter functions are automatically triggered.

When Vue.js initializes a component, it recursively converts the component's data object into getter/setter, and continuously monitors data changes. This monitoring mechanism is accomplished using a component called a "reactive system". Whenever a property in a data object is accessed or modified, the reactive system notifies all components that depend on that property to update their state.

3. How does Vue.js implement two-way data binding through data hijacking?

The way Vue.js implements two-way data binding is as follows:

3.1 v-model directive

The v-model directive is Vue.js’s implementation of two-way data binding. A simple way to determine. It allows developers to bind data model values ​​​​to view elements (such as input or textarea). When the value of a view element changes, the v-model directive automatically updates the corresponding value of the data model. Vice versa, when the value of the data model changes, the v-model directive automatically updates the view element bound to it. The following is an example of the v-model directive:

<input type="text" v-model="message" />

3.2 computed properties

Vue.js also provides a method of computed properties to implement two-way data binding. Computed properties are defined inside Vue.js components and their values ​​are derived from other properties. When the value of the property on which the calculated property depends changes, the value of the calculated property will also change. The following is an example of a computed property:

<template>
  <div>
    <input type="text" v-model="computedText" />
  </div>
</template>

<script>
export default {
  data() {
    return {
      text: "Hello World"
    };
  },
  computed: {
    computedText: {
      get() {
        return this.text;
      },
      set(newValue) {
        this.text = newValue;
      }
    }
  }
};
</script>

4. Summary

Vue.js’s two-way data binding mechanism can greatly simplify front-end development work and logic complexity. It completes data monitoring and synchronization in the form of data hijacking, and uses v-model instructions and calculated properties to provide convenient syntax sugar. This allows developers to interconnect application states and views to build interactive web applications and user interfaces.

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