What is Vue’s two-way binding subscriber?

In Vue.js, two-way data binding is one of its most important and distinctive features. The core technologies for implementing two-way data binding are dependency tracking and publish/subscribe patterns. In Vue.js, an object called Watcher plays a very important role. Its role is to notify the view layer of data changes and ensure the synchronization of data and views.

However, Watcher itself is not an independent entity, but is created in Dep (that is, the subscriber). The relationship between them is like the observers and topics in the publish/subscriber pattern.

So, what does each of them mean?

Watcher: Observer is responsible for subscribing to data changes. Once the data changes, it triggers an update operation and notifies the view layer to re-render.

Dep: Topic, data center, responsible for managing all Watchers and notifying Watchers to update when data changes.

Remember the data binding we used in Vue.js?

<template>
  <div>
    <input type="text" v-model="message">
    <h2>{{ message }}</h2>
  </div>
</template>
<script>
  export default {
    data () {
      return {
        message: 'Hello Vue!'
      }
    }
  }
</script>

In this example, we bind the data message to the <input> element, and also bind it synchronously to the < h2> element. This is how Vue.js two-way binding is used.

When we run this application, Vue.js starts to perform template compilation, analyzes the instructions in the template, and establishes a relationship diagram between DOM nodes and Watcher.

In other words, create a Watcher object on the <input> element, which will listen to message data changes and immediately update to the view layer.

In this process, the role of the Dep subscriber is reflected. When message data changes, it will notify all Watcher objects to perform update operations and let them re-render the view.

In general, the Dep subscriber is a very important part of the Vue.js framework. It works closely with the Watcher object to complete the core technology of two-way data binding in Vue.js.

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