Detailed explanation of the watchEffect feature in Vue3

watchEffectis a new feature provided in Vue3 to listen for changes in responsive data and execute specified callback functions when the data changes.

With Vue2watchdifferent,watchEffectInstead of specifying the data to be listened to, the responsive data used in the function will be automatically tracked and the callback function will be re-executeed when this data changes. This automatic tracking feature simplifies code and improves application performance.

Here is a usewatchEffectExample:

import { watchEffect, reactive } from 'vue'
const state = reactive({
  count: 0
})
watchEffect(() => {
  ()
})

In the above code, we usereactiveThe function creates a responsive objectstateand usewatchEffectListenChanges in attributes. whenWhen changes occur, the callback function will be re-execute.

It should be noted thatwatchEffectReturns a listener function that does not need to be stopped. If you need to stop listening, you can call this listener function to stop listening.

In addition to listening for changes in responsive data,watchEffectAlso supports accessing the context of a component in a callback function, e.g.thisComputational properties of keywords and components, etc.

Here is a usewatchEffectAn example of accessing component computed properties:

import { watchEffect, computed } from 'vue'
export default {
  computed: {
    doubleCount () {
      return  * 2
    }
  },
  mounted () {
    watchEffect(() => {
      ()
    })
  }
}

In the above code, we usecomputedThe function creates a computed propertydoubleCount, and inmountedUsed in hook functionswatchEffectListendoubleCountChanges. whendoubleCountWhen changes occur, the callback function will be re-execute.

Anyway,watchEffectIt is a very useful feature in Vue3. It allows us to easily listen for changes in responsive data and execute specified callback functions when the data changes, thereby simplifying code and improving application performance.

This is the end of this article about the detailed explanation of the watchEffect feature in Vue3. For more related Vue3 watchEffect content, please search for my previous articles or continue browsing the related articles below. I hope everyone will support me in the future!