Adding parameters to function

I just started to learn some oop and design patterns so I have this example:

function Img(imgId, imgSrc, imgClass) {
      this.imgId = imgId || '';
      this.imgSrc = imgSrc || '';
      this.imgClass = imgClass;
      
      let elm = document.createElement('img');
      elm.setAttribute('id', this.imgId);
      elm.setAttribute('src', this.imgSrc);
      elm.classList.add(this.imgClass);

      var xyz = document.getElementById('xyz');

      this.createImage = function() {
        xyz.appendChild(elm);
      }
    }

    var flowerImg = new Img('flower', 'http://ift.tt/2sLphk6', 'img').createImage();

    var airplane = new Img('airplane', 'http://ift.tt/2sLphk6', 'img img-wide').createImage();

<div action="" id="xyz">
      
  </div>

So if I try to use more than one class as function parameter, I get error.

I am trying to understand what and how to overcome it.