onload = function (el, callback) {
			if ('onload' in el) { // For standard browsers.
				el.onload = function () {
					callback();
				};
			} else if ('onreadystatechange' in el) { // For legacy IE.
				el.onreadystatechange = function () {
					var state = this.readyState;

					if (state === 'loaded' || state === 'complete') {
						el.onreadystatechange = null;
						callback();
					}
				};
			}
		}
Script element onload handler.
@param el {Object}
@callback {Function}