on_ready.js

on_ready.js

/**
	on_ready(callback)

	Run a function as soon as the DOM of a webpage is ready.
	The function may run immediately if the DOM is already ready.
	
	@param callback
		The function to run
*/
var on_ready = (function () {

	// Vars
	var callbacks = [],
		check_interval = null,
		check_interval_time = 250;

	// Check if ready and run callbacks
	var callback_check = function () {
		if (
			(document.readyState === "interactive" || document.readyState === "complete") &&
			callbacks !== null
		) {
			// Run callbacks
			var cbs = callbacks,
				cb_count = cbs.length,
				i;

			// Clear callbacks, events, checking interval
			callbacks = null;

			window.removeEventListener("load", callback_check, false);
			window.removeEventListener("DOMContentLoaded", callback_check, false);
			document.removeEventListener("readystatechange", callback_check, false);

			if (check_interval !== null) {
				clearInterval(check_interval);
				check_interval = null;
			}

			// Run callbacks
			for (i = 0; i < cb_count; ++i) {
				cbs[i].call(null);
			}

			// Okay
			return true;
		}

		// Not executed
		return false;
	};

	// Listen
	window.addEventListener("load", callback_check, false);
	window.addEventListener("DOMContentLoaded", callback_check, false);
	document.addEventListener("readystatechange", callback_check, false);

	// Callback adding function
	return function (cb) {
		if (callbacks === null) {
			// Ready to execute
			cb.call(null);
		}
		else {
			// Delay
			callbacks.push(cb);

			// Set a check interval
			if (check_interval === null && callback_check() !== true) {
				check_interval = setInterval(callback_check, check_interval_time);
			}
		}
	};

})();