Cannot read property 'addEventListener' of null Error, not sure why

Question

Whenever I hover over the image it does not enlarge and gives an error.

HTML and Javascript code(these are two separate files):

var banner = document.ge         


        

Answer 1

Your javascript code is in your first section. So it has rendered before banner element and cannot find the element id = banner because it has not rendered yet. Try to locate the code before the html code.

Answer 2

When referencing the function normalpic, you should preceed it with an empty function:

banner.addEventListener("mouseout",function(){normalpic},false)