mex_api/public/assets/datetimer/assets/table-of-contents.js

var table = document.querySelector(".c-r div"),
	list = table.querySelector(".c-r ol"),
	examples = document.getElementsByClassName("example"),
	header_height = document.querySelector(".hero").clientHeight,
	table_of_contents, table_of_scrolls = [];

function onScroll (e){
	if (window.pageYOffset > header_height - (e ? e.deltaY||16 : 16))
		table.classList.add("fixed");
	else
		table.classList.remove("fixed");

	highlightActive(e);
}

function highlightActive(e) {
	var currentActive = document.getElementsByClassName("current")[0];
	if (currentActive) {
		currentActive.className = ""
	}

	for (var i = table_of_scrolls.length - 1; i >=0; --i) {
		if (window.pageYOffset + (e ? e.deltaY : 0) >= table_of_scrolls[i]) {
			table_of_contents[i].classList.add("current");
			break;
		}
	}
}


function init() {
	for (var i = 0; i < examples.length; ++i) {
		var item = document.createElement("li"),
			link = document.createElement("a");

		item.innerHTML = "<span>"+ (i+1 + ". ") + "</span>";
		link.href="#"+examples[i].id;
		link.innerText=examples[i].getElementsByTagName("h3")[0].innerText||examples[i].getElementsByTagName("h2")[0].innerText;
		item.appendChild(link);
		list.appendChild(item);
		table_of_scrolls.push(window.pageYOffset + examples[i].getBoundingClientRect().top);
	}

	table_of_contents = list.querySelectorAll("li");

	onScroll();
	window.addEventListener("wheel", onScroll, {passive: true});
	list.addEventListener("click", function(e){
		var currentActive = document.getElementsByClassName("current")[0];
		if (currentActive) {
			currentActive.className = "";
		}

		e.target.parentNode.className = "current";
	});
}

function debounce(func, wait, immediate) {
	var timeout;
	return function() {
		var context = this, args = arguments;
		var later = function() {
			timeout = null;
			if (!immediate) func.apply(context, args);
		};
		var callNow = immediate && !timeout;
		clearTimeout(timeout);
		timeout = setTimeout(later, wait);
		if (callNow) func.apply(context, args);
	};
};

if (!/Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent))
	init();