How to automatically issue requests when data changes in Vue3

In Vue 3, data-driven is one of the very important concepts. Vue 3 implements the responsive principle through Proxy, which automatically re-renders components when data changes, thus achieving two-way binding of data and views.

However, in the actual development process, we often need to do other things when the data changes, such as sending Ajax requests. So how to automatically issue requests when data changes in Vue 3?

One way is to use the watchEffect function provided in Vue 3. This function receives one parameter, which is a function. This function contains the variables that need to be responded to. When these variables change, the watchEffect function will automatically trigger this function. For example:

import { watchEffect } from 'vue'

watchEffect(() => {
  // 需要响应的变量
  console.log('变量发生变化了')
})

In the above example, we use the watchEffect function to observe a variable. When the variable changes, the console will output "The variable has changed."

Next, we can send an Ajax request in the watchEffect function:

import { watchEffect } from 'vue'
import axios from 'axios'

watchEffect(() => {
  // 需要响应的变量
  axios.get('/api/data')
    .then(response => {
      // 处理响应的数据
    })
})

In the above example, when the responsive variable changes, the code in the watchEffect function will automatically execute , sends an Ajax request and processes the response data.

In addition to the watchEffect function, Vue 3 also provides the watch function. The watch function receives two parameters. The first parameter is the variable that needs to be monitored, and the second parameter is the callback function that needs to be executed when the variable changes. For example:

import { watch } from 'vue'
import axios from 'axios'

watch(
  // 监听的变量
  () => data.value,
  // 变量发生变化时执行的回调函数
  (newValue, oldValue) => {
    axios.get('/api/data')
      .then(response => {
        // 处理响应的数据
      })
  }
)

In the above example, when the data.value variable changes, the watch function will automatically execute the callback function, send the Ajax request and process the response data.

In short, whether we use the watchEffect function or the watch function, we can easily implement the function of automatically sending requests when the data changes, thereby making our applications more intelligent and efficient.

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