Simulate natural typing on a page

example.html

{{value | naturalType}}

naturalTyping.pipe.ts

@Pipe({name: 'naturalType', pure: false})
export class NaturalType {
   private typed: string = '';
   private target: string = '';
   private currentIndex: number = -1;
   private timeoutHandle: number = -1;
   constructor(
       private changeDetector: ChangeDetectorRef,
       private zone: NgZone,
   ) {
   }
   transform(value: string, mintypingSpeed: number = 30): any {
      if (this.target !== value) {
       clearTimeout(this.timeoutHandle);
       this.typed = '';
       this.currentIndex = -1;
       this.target = value;
       this.typeNextCharacter(mintypingSpeed);
      }
      return this.typed;
   }
   private typeNextCharacter(mintypingSpeed: number) {
    this.currentIndex++;
    this.typed = this.target.substr(0, this.currentIndex);
    this.changeDetector.markForCheck();
    if (this.typed !== this.target) {
      const time = Math.round(Math.random() * 70) + mintypingSpeed;
      this.timeoutHandle = setTimeout(()=> {
        this.zone.run(() => this.typeNextCharacter(mintypingSpeed));
      },time);
    }
   }
}