Uncaught TypeError: Cannot read properties of undefined (reading 'use')-CodePudding

I'm trying to start a new project using vue js. I think I have all the dependencies I need through the terminal. I installed npm, vue, vue-bootstrap and vue-router. Error is from line 7 on router.js, Vue.use(VueRouter).

Here's the code for my main.js

import Vue from "vue"
import App from "./App.vue"
import router from "./router.js"
import BootstrapVue from "bootstrap-vue"
import "bootstrap/dist/css/bootstrap.css"
import "bootstrap-vue/dist/bootstrap-vue.css"

Vue.use(BootstrapVue)

Vue.config.productionTip = false

new Vue({
  router,
  render: h => h(App),
}).$mount('#app')

Here's my router.js

import Vue from "vue"
import VueRouter from "vue-router"
import Home from "@/pages/Home.vue"
import About from "@/pages/About.vue"
import Contact from "@/pages/Contact.vue"

Vue.use(VueRouter)

export default new VueRouter({
  mode: 'history',
  base: process.env.BASE_URL,
  routes: [
    {
      path: '/',
      name: 'home',
      component: Home
    },
    {
      path: '/about',
      name: 'about',
      component: About
    },
    {
      path: '/contact',
      name: 'contact',
      component: Contact
    }
  
  ]
})

Sorry, I had the import vue line on the same line as the code indicators and it got cut off, I have the error still.

The full error is this:

router.js?41cb:7 Uncaught TypeError: Cannot read properties of undefined (reading 'use')
    at eval (router.js?41cb:7)
    at Module../src/router.js (app.js:1261)
    at __webpack_require__ (app.js:849)
    at fn (app.js:151)
    at eval (main.js:12)
    at Module../src/main.js (app.js:1141)
    at __webpack_require__ (app.js:849)
    at fn (app.js:151)
    at Object.1 (app.js:1274)
    at __webpack_require__ (app.js:849)
eval    @   router.js?41cb:7
./src/router.js @   app.js:1261
__webpack_require__ @   app.js:849
fn  @   app.js:151
eval    @   main.js:12
./src/main.js   @   app.js:1141
__webpack_require__ @   app.js:849
fn  @   app.js:151
1   @   app.js:1274
__webpack_require__ @   app.js:849
checkDeferredModules    @   app.js:46
(anonymous) @   app.js:925
(anonymous) @   app.js:928

CodePudding user response：

With vue 3 to create an app you must use the Vue.createApp method, and not create a new vue instance.

new Vue({
  router,
}).$mount('#app')

becomes:

const app = Vue.createApp({
      router,
})

app.mount('#app')

Remember that also the render api changed, while in 2 h was injected in the function args, now you have to import it from vue. Eg:

import { h } from 'vue'
export default {
  render() {
    return h('div')
  }
}

More infos on the docs: here.

Update. As requested in comments, I expand the example including how to use a plugin on vue 3.

Going back to the example up here, if we want to use a plugin we need to add the .use method BEFORE the mounting. Eg:

const app = Vue.createApp({
      router,
})
app.use(ThePluginIWantToUse)

app.mount('#app')

CodePudding user response：

Answer from Hiws:

BootstrapVue doesn't support Vue 3, so you'll have to either use Vue 2 or use another component library

Thanks.