domReady.js

/**
 * domReady for IE6+
 * @param  {Function} callback Callback
 *
 * @author http://beeker.io/jquery-document-ready-equivalent-vanilla-javascript
 * @date   2016-10-04
 */
function domReady(callback) {
	var ready = false;
	var detach = function() {
		if(document.addEventListener) {
			document.removeEventListener("DOMContentLoaded", completed);
			window.removeEventListener("load", completed);
		} else {
			document.detachEvent("onreadystatechange", completed);
			window.detachEvent("onload", completed);
		}
	};
	var completed = function() {
		if(!ready && (document.addEventListener || event.type === "load" || document.readyState === "complete")) {
			ready = true;
			detach();
			callback();
		}
	};

	if(document.readyState === "complete") {
		callback();
	} else if(document.addEventListener) {
		document.addEventListener("DOMContentLoaded", completed);
		window.addEventListener("load", completed);
	} else {
		document.attachEvent("onreadystatechange", completed);
		window.attachEvent("onload", completed);

		var top = false;

		try {
			top = window.frameElement == null && document.documentElement;
		} catch(e) {}

		if(top && top.doScroll) {
			(function scrollCheck() {
				if(ready) return;
				try {
					top.doScroll("left");
				} catch(e) {
					return setTimeout(scrollCheck, 50);
				}
				ready = true;
				detach();
				callback();
			})();
		}
	}
}