My scroll handler JavaScript doesn't work in Internet Explorer

Question

I have a script on my site that works in every browser, except Internet Explorer. Can someone explain why this doesn't work?

var header = document.getElementById('header');
var picturebg = document.getElementsByClassName('picturebg')[0];
var arrow = document.getElementsByClassName('toTop-transparent')[0];
var supportPageOffset = window.pageXOffset !== undefined;

window.onscroll = function() {
  "use strict";
  var y = window.scrollY;

  if (y > 7) {
    header.className = 'header-colored';
    arrow.className = 'toTop';
    picturebg.className = 'picturebgns';
  } else {
    header.className = 'header-transparent';
    arrow.className = 'toTop-transparent';
    picturebg.className = 'picturebg';
  }
};

The console doesn't give any errors, it just doesn't work. I have another jQuery script that runs just fine.

I've seen the other question here about the same thing, but it didn't help in any way.

Answer 1

Certain properties used in your snippet are not supported by IE.

From the MDN page on scrollY:

For cross-browser compatibility, use window.pageYOffset instead of window.scrollY. Additionally, older versions of Internet Explorer (< 9) do not support either property and must be worked around by checking other non-standard properties.¹

It appears you already have found the check for pageOffset support, so also check if non-standard properties are supported (e.g. CSS1 is compatible):

var isCSS1Compat = ((document.compatMode || "") === "CSS1Compat");

var y = supportPageOffset ? window.pageYOffset : isCSS1Compat ? document.documentElement.scrollTop : document.body.scrollTop;

Try this sample, using addEventListener() instead of onscroll.

var header = document.getElementById('header');
var picturebg = document.getElementsByClassName('picturebg')[0];
var arrow = document.getElementsByClassName('toTop-transparent')[0];
var supportPageOffset = window.pageXOffset !== undefined;
var isCSS1Compat = ((document.compatMode || "") === "CSS1Compat");



header.addEventListener('scroll', function(event) {
  "use strict";
  var y = supportPageOffset ? window.pageYOffset : isCSS1Compat ? document.documentElement.scrollTop : document.body.scrollTop;
console.log('y: ',y);
  if (y > 7) {
    header.className = 'header-colored';
    arrow.className = 'toTop';
    picturebg.className = 'picturebgns';
  } else {
    header.className = 'header-transparent';
    arrow.className = 'toTop-transparent';
    picturebg.className = 'picturebg';
  }
});

<div id="header" style="height: 50px; overflow: scroll;">
  <img  class="picturebg" src="https://www.gravatar.com/avatar/684fa9ff80577cbde88ffbdebafac5b4?s=32&d=identicon&r=PG&f=1" />
  <div id="arrow" class="toTop-transparent">&darr;</div>
  </div>

---

¹https://developer.mozilla.org/en-US/docs/Web/API/Window/scrollY#Notes