How to use Vue.prototype or global variable in Vue 3?

Like the title, I want to add Axios into Vue prototype. So when I want to use it, I can use it like this.$axios instead of importing it every time.

CODE:

//plugins/axios.ts import axios from 'axios' import router from '../router/index' const errorHandle = (): void => {}; const instance = axios.create({ // baseURL: process.env.NODE_ENV == 'development' ? '' : '' baseURL: ' timeout: 1000 * 12 }); instance.defaults.headers.post['Content-Type'] = 'application/x-www-form-urlencoded;charset=UTF-8' export default instance 

import { createApp } from 'vue' import App from './App.vue' import installElementPlus from './plugins/element' import instance from './plugins/axios' import router from './router' const app = createApp(App).use(router) installElementPlus(app) // app.config.globalProperties.http = instance app.config.globalProperties.$axios= instance app.mount('#app') 

However, there is a problem when I try to use it like this: this.$axios.

TS2339: Property '$axios' does not exist on type 'ComponentPublicInstance<{}, {}, {}, {}, {}, EmitsOptions, {}, {}, false, ComponentOptionsBase<{}, {}, {}, {}, {}, ComponentOptionsMixin, ComponentOptionsMixin, EmitsOptions, string, {}>>'. 

How could I fix this problem?

2 Answers

You could use provide/inject or define a global config property, which replaces Vue.prototype in Vue 3:

1. provide/inject (for Composition or Options API)

Provide

import axios from 'axios'; const app = Vue.createApp(App); app.provide('$axios', axios); // Providing to all components during app creation 

Inject

Composition API:

const { inject } = Vue; ... setup() { const $axios = inject('$axios'); // injecting in a component that wants it // $axios.get(...) } 

Options API:

inject: ['$axios'], // injecting in a component that wants it 

2. Global config (for Options API)

import axios from 'axios'; const app = Vue.createApp(App); app.config.globalProperties.$axios = axios; 

Options API:

this.$axios 

^{Note: This is only for the Options API. Evan You (Vue creator) says: "config.globalProperties are meant as an escape hatch for replicating the behavior of Vue.prototype. In setup functions, simply import what you need or explicitly use provide/inject to expose properties to app."}

There is a way to use globalProperties inside a setup function. Although this might be considered an anti-patter. It would be better to use provide/inject if possible. But if there is a library that uses globalProperties and you really need to access it from setup this is how you could do it.

<script setup> import { getCurrentInstance } from 'vue' const app = getCurrentInstance() const progressBar = app.appContext.config.globalProperties.$Progress progressBar.start() </script>