Javascript error - Touchstart - [Violation] Added non-passive event listener to a scroll-blocking 'touchstart' event

I'm getting the following error in the console referencing my mobile swipe script.

Error: [Violation] 
    Added non-passive event listener to a scroll-blocking 'touchstart' event. 
    Consider marking event handler as 'passive' to make the page more responsive. 

Below is the code snippet:

class Swipe {
    constructor(element) {
        this.xDown = null;
        this.yDown = null;
        this.element = typeof(element) === 'string' ? document.querySelector(element) : element;

        this.element.addEventListener('touchstart', function(evt) {
            this.xDown = evt.touches[0].clientX;
            this.yDown = evt.touches[0].clientY;
        }.bind(this), false);
    }

I ran across another article on this site that said to add the following:

document.addEventListener('touchstart', handler, {passive: true});

I've tried every possible way to implement this code into what I have with no success. When I try to add this statement it breaks my slider.

How would I go about adding this or inserting it into what I have already?

from Javascript error - Touchstart - [Violation] Added non-passive event listener to a scroll-blocking 'touchstart' event