[Dilettante_Pro]

В Chrome и IE11 ведет себя совершенно одинаково.

<style>
.is-fixed {
   position:fixed;
   top:10px;
   left:200px;
}
button {
   position:relative;
}
</style>
<div style="height:200px; width:300px;background-color:yellow"></div>
<button>Button</button>
<div style="height:200px; width:300px;background-color:green"></div>
<script>
var shareButtons = document.querySelector('button');
var coords = shareButtons.getBoundingClientRect();
var coordsTop = coords.top;

window.addEventListener("scroll", initSticky, false);

function initSticky() {
    let wScroll = window.pageYOffset;

    if (wScroll > coordsTop) {
        shareButtons.classList.add('is-fixed');
    } else {
        shareButtons.classList.remove('is-fixed');
    }
}
</script>