How to call event handler onload for Angular application?

I want to open a window containing user authorization form details. I want to do this by checking window location, to do so the event handler not call on every event.  I am not able to overwrite event handlers.

Why the event is not triggering? what could be the alternative way to intercept the Authorization form result?

My code:

import { Inject, Injectable } from '@angular/core';// ... other imports will be go here. //@Injectable({ providedIn: 'root'})export class UserWindowService { constructor(@Inject(WINDOW) public window: Window) {} // here WINDOW is imported from InjectionToken<Window> openUserWindow(): void { let windowObj = this.window.open('//localhost:4200/verify', '_blank'); let evntHandler= function() { console.log(windowObj!.location); }; //Below order of events should execute one by one, one after one. windowObj!.onload = evntHandler; windowObj!.addEventListener('load', evntHandler); windowObj!.addEventListener('onload', evntHandler); windowObj!.document.onload = evntHandler; windowObj!.onhashchange = evntHandler; windowObj!.addEventListener('hashchange', evntHandler, false); }}