cmc_fe/src/App.vue

<template>
    <CMCApp :class="{ fadein : !isLoading }" v-if="!isLoading" />
    <LoadingScreen :isLoading="isLoading" />
</template>
<script>
import CMCApp from './CMCApp.vue'
import LoadingScreen from "./components/LoadingScreen.vue"
export default {
    data(){
        return {
            isLoading: true
        }
    },
    components: {
        CMCApp,
        LoadingScreen
    },
    mounted(){
        setTimeout(() => {
            this.isLoading = false;
        },3000);
    }
}
</script>
<style>
.fadein {
  animation: fadein 1s forwards;
}

@keyframes fadein {
    from {
        opacity:0;
        visibility:hidden;
    }
    to {
        opacity:1;
        visibility:visible;
    }
}
</style>