vue.esm.js?efeb:591 [Vue warn]: Error in mounted hook:

前言：在vue项目中使用pubsub发生错误

** vue.esm.js?efeb:591 [Vue warn]: Error in mounted hook: "ReferenceError: PubSub is not defined" **

原因1：未安装pubsub

1.参照官网地址安装：https://www.npmjs.com/package/pubsub-js

Getting PubSubJS

There are several ways of getting PubSubJS

• Install via npm (npm install pubsub-js)
• Use it directly from a CDN directly
  • http://www.jsdelivr.com/#!pubsubjs
  • https://cdnjs.com/libraries/pubsub-js
  • https://unpkg.com/pubsub-js
• Download a tagged version from GitHub

2.首先必须导入模块：

import PubSub from 'pubsub-js'

3.运行出现问题 This dependency was not found:执行如下命令

npm install --save .pubsub-js

如果上面都没有问题正好是在watch中调用不能使用this，如下就会出错

vue.esm.js?efeb:1741 TypeError: Cannot read property 'publish' of undefined

• 错误代码

watch: {
    test(val) {
     //注意：这是错误代码
      this.PubSub.publish("test", val);
    }
  }

• 正确代码

watch: {
    test(val) {
    //正确代码
      PubSub.publish("test", val);
    }
  }

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