5 - watch 全家桶

[sly3464]

<script setup lang="ts">
import { ref, watch } from "vue"

const count = ref(0)

/**
 * Challenge 1: Watch once
 * Make sure the watch callback only triggers once
*/
const stop = watch(count, () => {
  console.log("Only triggered once");
  stop()
});

count.value = 1
setTimeout(() => count.value = 2)

/**
 * Challenge 2: Watch object
 * Make sure the watch callback is triggered
*/
const state = ref({
  count: 0,
})

watch(state.value, () => {
  console.log("The state.count updated")
})
// OR
// watch(state, (value) => {
//   console.log("The state.count updated")
// }, { deep: true })

state.value.count = 2

/**
 * Challenge 3: Callback Flush Timing
 * Make sure visited the updated eleRef
*/

const eleRef = ref()
const age = ref(2)
watch(age, () => {
  console.log(eleRef.value)
},{flush: 'post'})
age.value = 18

</script>

<template>
  <div>
    <p>
      {{ count }}
    </p>
    <p ref="eleRef">
      {{ age }}
    </p>
  </div>
</template>