1.綁定

function(element, type, handler){
if (element.addEventListener) {
element.addEventListener(type, handler, false);
}
else
if (element.attachEvent) {
element.attachEvent("on" + type, handler);
}
else {
element["on" + type] = handler;
}
}

2.刪除

function(element, type, handler){
if (element.removeEventListener) {
element.removeEventListener(type, handler, false);
}
else
if (element.detachEvent) {
element.detachEvent("on" + type, handler);
}
else {
element["on" + type] = null;
}
}

3.阻止默認事件

function(event){
if (event.preventDefault) {
event.preventDefault();
}
else {
event.returnValue = false;
}
}

4.不傳播事件（阻止冒泡）

function(event){
if (event.stopPropagation) {
event.stopPropagation();
}
else {
event.cancelBubble = true;
}
}

5.獲得event的target

function(event){
return event.target || event.srcElement;
}

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