Vue.js 3 - Error while using Vue I18n plugin in vue - Cannot set property '_vm' of undefined

Question

I've just started working with Vue.js and learning it through some online code snippet and tutorials. I'm trying to implement internationalization support for my vue project, but I'm getting error in web-console.

Here are my code snippets

main.js

import { createApp } from 'vue';
import App from './App.vue';
import VueI18n from 'vue-i18n'
import router from './router/index'

function loadLocaleMessages () {
    const locales = require.context('./locales', true, /[A-Za-z0-9-_,\s]+\.json$/i)
    const messages = {}
    locales.keys().forEach(key => {
        const matched = key.match(/([A-Za-z0-9-_]+)\./i)
        if (matched && matched.length > 1) {
            const locale = matched[1]
            messages[locale] = locales(key)
        }
    })
   return messages
}

const i18n = VueI18n({
    locale: process.env.VUE_APP_I18N_LOCALE || 'en',
    fallbackLocale: process.env.VUE_APP_I18N_FALLBACK_LOCALE || 'en',
    messages: loadLocaleMessages()
})


const app = createApp(App);
app.use(router);
app.use(i18n);
app.mount('#app');

Here is my HelliI18n.vue file where I want to use translation

<template>
    hello
    <p>{{ $t('hello') }}</p>
</template>

<script>
    export default {
        name: 'HelloI18n'
    }
</script>

Following code is from my package.json file (for versions)

"dependencies": {
    "core-js": "^3.6.5",
    "vue": "^3.0.0",
    "vue-i18n": "^8.22.1",
    "vue-router": "^4.0.0-0"
},
"devDependencies": {
    "@intlify/vue-i18n-loader": "^1.0.0",
    "@vue/cli-plugin-babel": "~4.5.0",
    "@vue/cli-plugin-eslint": "~4.5.0",
    "@vue/cli-plugin-router": "~4.5.0",
    "@vue/cli-service": "~4.5.0",
    "@vue/compiler-sfc": "^3.0.0",
    "babel-eslint": "^10.1.0",
    "eslint": "^6.7.2",
    "eslint-plugin-vue": "^7.0.0-0",
    "vue-cli-plugin-i18n": "~1.0.1"
},

When I run my project, I see following error on web console

Uncaught TypeError: Cannot set property '_vm' of undefined
at VueI18n (vue-i18n.esm.js?a925:1173)
at eval (main.js?56d7:19)
at Module../src/main.js (app.js:1167)
at __webpack_require__ (app.js:854)
at fn (app.js:151)
at Object.1 (app.js:1228)
at __webpack_require__ (app.js:854)
at checkDeferredModules (app.js:46)
at app.js:994
at app.js:997

Anything I'm doing wrong here ? any dependency I'm missing ? Any help would be really appreciated.

Answer 1

You should install vue-i18n@next which is compatible with Vue 3:

 npm install --save vue-i18n@next

or via using yarn

yarn add vue-i18n@next

Basic usage :

import { createApp } from "vue";
import App from "./App.vue";

import { createI18n } from "vue-i18n";

const i18n = createI18n({
  legacy: false,
  locale: "ja",
 globalInjection: true,
  messages: {
    en: {
      message: {
        language: "English",
        greeting: "Hello !"
      }
    },
    ar: {
      message: {
        language: "العربية",
        greeting: "السلام عليكم"
      }
    },
    es: {
      message: {
        language: "Español",
        greeting: "Hola !"
      }
    }
  }
});

createApp(App).use(i18n).mount("#app");

App.vue

<template>
  <div>
    <select v-model="lang">
      <option value="en">English</option>
      <option value="ar">العربية</option>
      <option value="es">Español</option>
    </select>

    <h2>{{ $t("message.greeting", {}, { locale: lang }) }}</h2>
  </div>
</template>
<script>
export default {
  data() {
    return {
      lang: "en",
    };
  },
};
</script>

EXAMPLE

In composition API (setup) :

import { useI18n } from 'vue-i18n';
...

export default defineComponent({
    setup() {
        const { t } = useI18n();
      // then use it like t('message.greeting')
  }
})