使用vue.js怎么定义全局变量

<!--设置全局变量-->
<script>
    //接口地址
    const BASE_URL = 'http://118.189.105.152:7181/qianzhang-transf/index/'; //定义全局接口地址
    //请求头部       
    const reqHead = { 
        "transDate": "20180816",
        "encryptFlag": "1",
        "seqNo": "2018081628507127",
        "serviceID": "loanLmtQryHXMKL",
        "transTime": "174341",
        "channelID": "netbank"
    }
    export default {   //将常量暴露出去
        BASE_URL,
        reqHead,
    }
</script>

// The Vue build version to load with the `import` command
// (runtime-only or standalone) has been set in webpack.base.conf with an alias.
import Vue from 'vue'
import App from './App'
import router from './router'
import fastclick from 'fastclick'
import global_ from './components/Global.vue'  //引入全局组件
Vue.prototype.GLOBAL = global_;  //修改原型
Vue.config.productionTip = false
/* eslint-disable no-new */
new Vue({
  el: '#app',  
  router, 
  components: { App },
  template: '<App/>'
})