Convert all scrolling to horizontal scrolling

scroll-horizontal.js

// Make vertical mousewheel movement scroll a page horizontally.
//
// Seems to work well with Mac trackpads and Magic Mouse on macOS.
// Also works with either scroll direction on macOS.

// If body has class 'scroll-horizontal'
if(document.body.className.split(' ').indexOf('scroll-horizontal') !== -1) {
	['wheel', 'mousewheel', 'DOMMouseScroll'].forEach(function(eventName) {
		// Test for browser support of event
		if(typeof window['on' + eventName] !== 'undefined') {
			window.addEventListener(eventName, function(e) {
				// If scroll has both horizontal and vertical components, use the greater absolute value
				var scrollAmount = Math.abs(e.deltaY) > Math.abs(e.deltaX) ? e.deltaY : e.deltaX;
				window.scrollBy(scrollAmount, 0);
				e.preventDefault();
			});
		}
	});
}