Microsoft AJAX Library Cheat Sheet（4）：DomEvent类

本文为翻译，英文原版的Cheat Sheet（PDF版本）在此下载：http://aspnetresources.com/downloads/ms_ajax_library_cheat_sheets1.zip

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注：标注有[S]的为静态方法，无须实例化对象即可使用。

 

[S] addHandler (element, eventName, handler)
[S] $addHandler (element, eventName, handler)

为DOM元素添加某一事件的处理函数，事件名称应去掉“on”前缀。

注意：在事件处理函数中，this指向的是element，而不一定是发出该事件的元素。

Sys.UI.DomEvent.addHandler (element, "click", clickHandler);

// Same as $addHandler (element, "click", clickHandler);

function clickHandler (e) { … }

 

[S] addHandlers (element, events, handlerOwner)
[S] $addHandlers (element, events, handlerOwner)

为DOM元素添加多个事件处理函数，events是一个事件处理函数的字典。

注意：在事件处理函数中，若指定了handlerOwner，那么this将指向该handlerOwner，否则将指向element。

$addHandlers ($get ("article"), {

    mouseover: onMouseOver,

    mouseout: onMouseOut

});

function onMouseOver (e) { this.style.backgroundColor = 'yellow'; }

function onMouseOut (e) { this.style.backgroundColor = 'white'; }

 

[S] clearHandlers (element)
[S] $clearHandlers (element)

移除指定DOM元素所有的事件处理函数。

Sys.UI.DomEvent.clearHandlers (element);

// Same as $ clearHandlers (element);

 

[S] removeHandler (element, eventName, handler)
[S] $removeHandler (element, eventName, handler)

为DOM元素移除指定的事件处理函数。

Sys.UI.DomEvent.removeHandler (element, "click", clickHandler);

// Same as $removeHandler (element, "click", clickHandler);

 

preventDefault ()

阻止执行默认的事件处理函数。例如若阻止了a元素的onclick事件，那么将不会引发页面导航。

$addHandler ($get ("showMoreLink"), "click", showMore);

function showMore (e) { e.preventDefault (); }

 

stopPropagation ()

阻止事件冒泡传递至父元素。

 

Event对象的属性

1. altKey：判断触发事件时Alt键是否被按下。
2. button：得到触发事件的鼠标按键。可选值为Sys.UI.MouseButton枚举（leftButton、middleButton和rightButton）。
3. charCode：得到触发事件时的键盘按键代码。可以为Sys.UI.Key枚举（backspace, tab, enter,esc, space, pageUp, pageDown, end, home, left, up, right, down, del）。
4. clientX：鼠标指针相对于文档可见区域的X坐标。
5. clientY：鼠标指针相对于文档可见区域的Y坐标。
6. ctrlKey：判断触发事件时Ctrl键是否被按下。
7. offsetX：鼠标指针相对于触发事件元素左侧边缘的偏移位置。
8. offsetY：鼠标指针相对于触发事件元素上边缘的偏移位置。
9. rawEvent：原始的DOM事件。
10. screenX：鼠标指针相对于浏览者屏幕的X坐标。
11. screenY：鼠标指针相对于浏览者屏幕的Y坐标。
12. shiftKey：判断触发事件时Shift键是否被按下。
13. target：触发事件的对象。
14. type：事件名称（例如“click”）。