import { Component, OnDestroy, OnInit } from "@angular/core"; import * as screenfull from "screenfull"; @Component({ selector: "my-fullscreen-button", templateUrl: "fullscreen-button.component.html", styleUrls: ["fullscreen-button.component.scss"], }) export class FullscreenButtonComponent implements OnDestroy, OnInit { public isFullscreen = false; private listener = null; constructor() { // Do stuff } public ngOnInit(): void { this.listener = screenfull.on("change", () => { this.isFullscreen = screenfull.isFullscreen; }); this.isFullscreen = screenfull.isFullscreen; } public ngOnDestroy(): void { if (this.listener) { screenfull.off(this.listener); } } }