Listen for passwords while on page

TypeingListen.ts

import { Injectable, EventEmitter } from '@angular/core';

@Injectable()
export class TypeingListen extends EventEmitter<boolean> {
    
    private keyStack:string[] = [];

    private emptyInterval:any;

    constructor( private password:String ) {
        super();
        window.addEventListener('keyup', this.onKeyDown.bind(this));
    }

    private cleanStack():void {
        this.keyStack.length = 0;
    }

    private validate():void {
        if (this.keyStack.join('') === this.password.toUpperCase() ) {
            this.emit(true);
        }
    }

    private onKeyDown( event:KeyboardEvent ):void {
        
        this.keyStack.push(
            String.fromCharCode(event.keyCode)
        );

        this.validate();

        if (this.emptyInterval) {
            clearTimeout(this.emptyInterval);
        }

        this.emptyInterval = setTimeout(this.cleanStack.bind(this), 1000);
    }
}