Make the project banner on a repository page sticky as you scroll down (new ui only)

StickyGithubHeader.js

(function() {
    var $ = function(str) {
        return document.querySelector(str);
    };
    var win = window;
    var doc = document.documentElement;
    
    var mast = $('#js-repo-pjax-container .pagehead');
    var mastTop = mast.offsetTop;
    var adjustedMargin = mast.offsetHeight;

    var currentMastAttributes = mast.getAttribute('style');
    var newMastAttributes = [
        currentMastAttributes,
        'position: fixed;',
        'z-index: 10;',
        'top: 0;',
        'left: 0;',
        'right: 0;'
    ].join('');

    var content = $('#js-repo-pjax-container .repo-container');
    var currentContentAttributes = content.getAttribute('style');
    var newContentAttributes = [
        currentContentAttributes,
        'margin-top: ' + adjustedMargin + 'px;'
    ].join('');

    var toggle = false;
    document.addEventListener('scroll', function() {
        var scrollTop = (win.pageYOffset || doc.scrollTop)  - (doc.clientTop || 0);
        if (scrollTop > mastTop) {
            content.setAttribute('style', newContentAttributes);
            mast.setAttribute('style', newMastAttributes);

            toggle = true;

            setTimeout(function() {toggle = false}, 100);
        } else if (!toggle) {
            content.setAttribute('style', currentContentAttributes);
            mast.setAttribute('style', currentMastAttributes);
        }
    });
}());