14-7-4 將 localStorage 做成 plugin

1. localStorage的用法：
   1. https://developer.mozilla.org/zh-TW/docs/Web/API/Window/localStorage
   2. https://medium.com/%E9%BA%A5%E5%85%8B%E7%9A%84%E5%8D%8A%E8%B7%AF%E5%87%BA%E5%AE%B6%E7%AD%86%E8%A8%98/javascript-localstorage-%E7%9A%84%E4%BD%BF%E7%94%A8-e0da6f402453
2. 建立plugin/localStorage.js

   export default ({ app }, inject) => {
     inject("localStorage", {
       set(key = "", val = {}) {
         localStorage.setItem(key, JSON.stringify(val));
       },
       get(key = "") {
         const obj = JSON.parse(localStorage.getItem(key));
         // 避免傳回 null
         if (!obj) {
           return {};
         }
         return obj;
       },
       remove(key = "") {
         localStorage.removeItem(key);
       },
       removeAll() {
         localStorage.clear();
       }
     });
   };
   

    

3. 加入nuxt.config.js設定

     plugins: [
       "~/plugins/hello.js",
       "~/plugins/axios.js",
       "~/plugins/notification.js",
       "~/plugins/localStorage.js"
     ],

    

4. 如此，便可方便的localStorage使用

     mounted() {
       this.$hello("我在前端被mounted了");
       this.$localStorage.set("userData", { name: "tad", age: 48 });
       console.log('userData', this.$localStorage.get("userData"));
     },