详解Vue3如何优雅的监听localStorage变化
作者：萌萌哒草头将军
最近在研究框架，也仔细用了Vue3一些功能，所以本文就来和大家聊聊Vue3如何实现优雅的监听localStorage的变化，感兴趣的小伙伴可以跟随小编一起学习一下
为什么要这样做
原生的localStorage只能监听同源地址下不同页面的localStorage变化，作为单页面应用，显然不实用。所以我打算自定义一个hook监听localStorage的变化。
思路
首先我们需要重写localStorage下的所有方法，这样在每个方法被使用的时候就可以被监听到了。
此时就需要一个事件机制，用于传递消息。
在Vue3移除了$on、$emit事件接口后，我们可以借助第三方库实现：mitt、tiny-emitter.
不过我打算使用自己实现的中介者模式作为通信方法。
实现
实现中介者模式
// mediator.ts
export interface MediatorProps {
uuid?: number;
publish?: (topic: string, ...args: unknown[]) => void;
subscribe?: (topic: string, callback: (...args: unknown[]) => void) => void;
}
const mediator = (function () {
let topics = [],
uuid = 0;
function subscribe(topic: string, callback: (...args: unknown[]) => void) {
uuid++;
topics[topic] = topics[topic]
? [...topics[topic], { callback, uuid }]
: [{ callback, uuid }];
}
function publish(topic: string, ...args: unknown[]) {
if (topics[topic]) {
topics[topic].map((item) => item.callback(...args));
}
}
return {
install: function (obj: MediatorProps) {
obj.uuid = uuid;
obj.publish = publish;
obj.subscribe = subscribe;
return obj;
},
};
})();
export default mediator;重写localStorage
// localStorage.ts
import mediator from "./mediator";
const keys: string[] = [];
const createMediator = () => mediator.install({});
const sub = createMediator();
export const $localStorage = {
getItem: (key: string) => {
return window.localStorage.getItem(key);
},
setItem: (key: string, value: any) => {
// 防止重复发布
if (!keys.includes(key)) keys.push(key);
// 被修改就发布事件
sub.publish(key, value);
window.localStorage.setItem(key, value);
},
clear: () => {
// 被删除就每个key发布事件
keys.map((key) => sub.publish(key, undefined));
// 发布后清空记录key的数组
keys.length = 0;
window.localStorage.clear();
},
removeItem: (key: string) => {
keys.splice(keys.indexOf(key), 1);
// 被移除就发布 undefined
sub.publish(key, undefined);
window.localStorage.removeItem(key);
},
key: window.localStorage.key,
length: window.localStorage.length,
};实现useStorage hook
// useStorage.ts
import { ref } from "vue";
import mediator from "./mediator";
const createMediator = () => mediator.install({});
export const useStorage = (key: string) => {
const string = ref(null);
const sub = createMediator();
sub.subscribe(key, (value) => string.value = value);
return string;
};测试
使用localStorage
// One.vue
// 使用localStorage
import { watch } from "vue";
import { useStorage } from "./hook";
const key = useStorage("yourKey");
watch([key], (a) => console.log(a));监听localStorage变化
// Two.vue
// 监听localStorage
<script setup lang="ts">
import { ref } from "vue";
import { localStorage } from "./hook";
const count = ref(0);
</script>
<template>
<div>
<button
type="button"
@click="$localStorage.setItem('a', count++);"
>
count is {{ count }}
</button>
</div>
</template>结果
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