Vue template or render function not defined

Question

I have problem with Vue rendering on my website. I have downloaded some forum app from github , I had some difficoulties with installing it, because npm is not really updated and app is from 2 years ago. I managed to fix everything about npm with package.json like:

"devDependencies": {
        "axios": "^0.18.1",
        "bootstrap": "^4.4.1",
        "cross-env": "^5.2.1",
        "jquery": "^3.5.0",
        "laravel-mix": "^5.0.4",
        "lodash": "^4.17.15",
        "popper.js": "^1.16.1",
        "resolve-url-loader": "^3.1.1",
        "sass-loader": "^8.0.2",
        "vue": "2.5.21",
        "vue-template-compiler": "2.5.21"
    },
    "dependencies": {
        "laravel-echo": "^1.7.0",
        "node-sass": "^4.13.1",
        "pusher-js": "^4.4.0",
        "vue-loader": "15.5.1",
        "vue-router": "^3.1.6",
        "vue-simplemde": "^1.0.4",
        "vuetify": "^1.5.24"
    }

But now the problem is something with rendering vue:

app.js:71622 [Vue warn]: Failed to mount component: template or render function not defined.

This is how app.js looks like:

require('./bootstrap');

window.Vue = require('vue');
import Vue from 'vue'
import Vuetify from 'vuetify'
import VueSimplemde from 'vue-simplemde'
import 'simplemde/dist/simplemde.min.css'


Vue.use(Vuetify)
Vue.use(VueSimplemde)
import md from 'marked'
window.md = md;

import User from './Helpers/User'
window.User = User

import Exception from './Helpers/Exception'
window.Exception = Exception

window.EventBus = new Vue();

/**
 * Next, we will create a fresh Vue application instance and attach it to
 * the page. Then, you may begin adding components to this application
 * or customize the JavaScript scaffolding to fit your unique needs.
 */

Vue.component('AppHome', require('./components/AppHome.vue'));
import router from './Router/router.js'

const app = new Vue({
    el: '#app',
    router
});

Answer 1

You are getting that error because your App has no render template specified at all, new Vue() is missing render option called Render Function .

This would contain the minimum required HTML for the app to work where most importantly: <div id="app"></div> is required because the el option set to #app is telling Vue what html element it should mount it's self to when rendering.

The most common way of of providing the instance with a template is to have a dedicated component that would be home to apps top level html layout but the minimum requirement is as follows:

// App.vue

<template>

  <div id="app"></div>

</template>

// app.js

import Vue from 'vue'
import App from './App.vue' // <-- MAIN TEMPLATE
import router from './router'

const app = new Vue({
  el: '#app',
  render: h => h(App), // <-- REGISTER MAIN TEMPLATE
  router
});

However since this source appears to be a Laravel Project, clearly the HTML is in a blade template rendered server side and I always find Laravel rendering Vue components server side to be a wonkey concept, I prefer an SPA with Laravel Acting as an API.

Perhaps this resource will help https://vuejsdevelopers.com/2017/11/06/vue-js-laravel-server-side-rendering/