js detec when mouse leaves element code example

Example 1: mouseout vs mouseleave js event

The mouseout event triggers when the mouse pointer leaves any
child elements as well the selected element.
The mouseleave event is only triggered when the mouse pointer 
leaves the selected element.

Example 2: mouseleave to original image

function createHover (that) {

  var original = document.getElementsByClassName("image_left"); // attempt

  that.addEventListener('mouseover', function() {
    var src = that.getAttribute('data-src');
    if (src) {
      imageContainer.src = src;
    }
  });
  that.addEventListener('mouseleave', function() {
    // imageContainer.src = original;
  });
}

  initImageHover('li.one > a');
});