Declaring custom instance properties in Vue 3 and typescript

vue 3 custom properties.md

//declare the property so that it can be used by ts
declare module '@vue/runtime-core' {
    interface ComponentCustomProperties {
        $socket: SocketIOClient.Socket;
    }
}

const app = createApp(App)
//mount app with the vue 3 global properties  api
app.config.globalProperties.$socket = socket;
app.mount('#app')