Unable to pass object property to IIFE inside constructor function

Question

I have created a boxInfo object below. Inside it, I have created a function, leftPos which is an IIFE and I am passing the value to this function. However, I am getting undefined. When I simply pass this, it manages to pass the whole object. But when I try to narrow down, using dot operator it returns undefined.

I am trying to pass

SimpleShow.init = function (el, options) {
        self = this;
        //Selects the slider box
        self.box = document.querySelector(el);
        //Creates the array of all the items in the slider
        self.slides = document.querySelector(el + "> ul").children;

        //facing the problem below
        self.boxInfo = {
            heightBox: self.box.offsetHeight,
            widthBox: self.box.offsetWidth,

            //trying to pass this proeprty to function below
            totalWidth: self.box.offsetWidth * self.slides.length,

            //Calculates the starting points for each slides
            leftPos: ((totalWidth) => {
                //Testing what value is being passed inside - Getting undefined
                console.log(totalWidth);

            })(this.boxInfo.totalWidth) //this is not passing the property
        }

        initBox(self.box, self.slides, self.boxInfo );
        startSlideShow();
    }