//首先准备好常规的事件绑定函数
function addEvent(element, name, callback) {
	//标准浏览器
	if(element.addEventListener) element.addEventListener(name, callback, false);
	//IE
	else element.attachEvent("on" + name, callback);
}
//双击按键绑定函数
function addDblPressEvent(element, callback) {
	var presstime = 2;//次数为2
	addEvent(element, "keyup", press);
	//每次单击触发
	function press(e) {
		presstime--;
		setTimeout(reset, 300);
		if(presstime === 0) fire(e);
	}
	//恢复计数器
	function reset() {
		presstime++;
	}
	//触发双击
	function fire(e) {
		callback.call(element, e);
	}
}

//试一下
window.onload = function() {
	addDblPressEvent(document, function(e) {
		console.log("double clicked");
	});
}