usefulness of `declare const`

src/App.vue

@@ -10,8 +10,6 @@
 
 <script lang="ts">
 import HelloWorld from "./components/HelloWorld.vue";
-console.log(APP_TITLE);
-console.log(APP_VERSION);
 export default {
   name: "App",
   components: {

src/main.ts

@@ -2,5 +2,6 @@ import { createApp } from 'vue'
 import App from './App.vue'
 import './index.css'
 
-document.title = APP_TITLE
-createApp(App).mount('#app')
+
+createApp(App).mount('#app')
+document.title = APP_TITLE

src/shims-vue.d.ts

@@ -3,3 +3,6 @@ declare module "*.vue" {
   const Component: ReturnType<typeof defineComponent>
   export default Component
 }
+
+declare const APP_VERSION: string
+declare const APP_TITLE: string