国际化
i18n意思就是i开头,n结尾,中间还有18个字母,23333
<script src="../node_modules/vue/dist/vue.js"></script>
<div id="app">
    <h1>{{ $t("welcome-message") }}</h1>
    <button @click="changeLang('en')">English</button>
    <button @click="changeLang('zh')">中文</button>
    <button @click="changeLang('nl')">Dutch</button>
</div>
<script>
    const i18nPlugin = {
        // Implement this!
        install(Vue, locales) {
            Vue.prototype.$t = function(id) {
                console.log(id);
                return locales[this.$root.lang][id];
            };
        }
    };
    Vue.use(
        i18nPlugin,
        /* option */ {
            en: { "welcome-message": "hello" },
            zh: { "welcome-message": "你好" },
            nl: { "welcome-message": "Hallo" }
        }
    );
    new Vue({
        el: "#app",
        data: {
            lang: "zh"
        },
        methods: {
            changeLang(lang) {
                this.lang = lang;
            }
        }
    });
</script>