When mounted focus on username input.

frontend/components/LoginPage.vue

@@ -7,6 +7,7 @@
         <input
           type="text"
           v-model="username"
+          ref="username"
           placeholder="Brukernavn"
           autocapitalize="none"
           @keyup.enter="submit"
@@ -34,6 +35,9 @@ export default {
       error: undefined
     };
   },
+  mounted() {
+    this.$refs.username.focus();
+  },
   methods: {
     submit() {
       login(this.username, this.password)