实现本地存储函数useLocalStorage

 我们经常需要使用 LocalStorage API，一个好用的可组合函数封装将帮助我们更好地使用它，让我们开始吧 👇:

<script setup lang='ts'>

import { ref, watch } from "vue"

/**
 * Implement the composable function
 * Make sure the function works correctly
*/
function useLocalStorage(key: string, initialValue: any) {
  const value = ref(initialValue)
  watch(value,(val)=>{
    localStorage.setItem(key,val)
  },{
    immediate:true
  })
  return value
}

const counter = useLocalStorage("counter", 0)

// We can get localStorage by triggering the getter:
console.log(counter.value)

// And we can also set localStorage by triggering the setter:

const update = () => counter.value++

</script>

<template>
  <p>Counter: {{ counter }}</p>
  <button @click="update">
    Update
  </button>
</template>

其中的watch可以修改为以下方式：

watchEffect(() => {
    localStorage.setItem(key, value.value)
})

// watchEffect自动添加了immediate:true

watchEffect：立即运行一个函数，同时响应式地追踪其依赖，并在依赖更改时重新执行。

watchEffect的特点可以查看watchEffect()和effectScope()-CSDN博客