debounce.directive.ts

import { EventEmitter, ElementRef, OnInit, Directive, Input, Output } from '@angular/core';
import { Observable } from 'rxjs';
import { NgModel } from '@angular/forms';

@Directive({ selector: '[debounce]' })
export class DebounceDirective implements OnInit {
    @Input() delay: number = 700;
    @Output() keyUpFunc: EventEmitter<any> = new EventEmitter();

    constructor(private elementRef: ElementRef, private model: NgModel) {
    }

    ngOnInit(): void {
        const eventStream = Observable.fromEvent(this.elementRef.nativeElement, 'keyup')
            .map(() => this.model.value)
            .debounceTime(this.delay);

        eventStream.subscribe(input => this.keyUpFunc.emit(input));
    }

}