vue3でグローバル変数を定義する方法

app.config.globalProperties.$systemId = "10"

import { getCurrentInstance } from "vue";
const systemId = getCurrentInstance()?.appContext.config.globalProperties.$systemId
console.log(systemId);//控制台可以看到输出了10

// 之前(Vue 2.x)
Vue.prototype.$http = () => {}
 
// 之后(Vue 3.x)
const app = Vue.createApp({})
app.config.globalProperties.$http = () => {}

import { getCurrentInstance, onMounted } from "vue";
export default {
  setup( ) {
    const { ctx } = getCurrentInstance(); //获取上下文实例，ctx=vue2的this
    onMounted(() => {
      console.log(ctx, "ctx");
      ctx.http();
    });
  },
};