Parallax with TypeScript

parallax.ts

class parallax {
    private _backgroundElement:string; 
    private _containerElement:string; 

    set containerElement(name: string){
        this._containerElement = name; 
    }
    set backgroundElement(name: string){
        this._backgroundElement = name; 
    }

    constructor() {  
        this.onTimeout();
    }
    private onTimeout(){
        setTimeout(()=>{
            this.onScroll(); 
        }, 0); 
    }
    private onScroll(){
        $(window).scroll(()=>{
            let elementOffset:number = $(this._containerElement).offset().top;
            let scrollYOffset:number = pageYOffset;
            let elementHeight:number = $(this._containerElement).height(); 
            let elementBottomOffset:number = scrollYOffset + elementHeight; 
        
        if ( scrollYOffset < elementBottomOffset){
            let elementScrollOffset:number = elementOffset - scrollYOffset;
            console.log(this._backgroundElement); 
            $(this._backgroundElement).css({'background-position-y': elementScrollOffset / 3 });
        }
        });
    }
}

let parallaxInstance = new parallax(); 
parallaxInstance.backgroundElement= ".spacer2"; 
parallaxInstance.containerElement = ".prices";