Javascript 主动派发事件

参考：

http://www.jb51.net/article/27971.htm

https://developer.mozilla.org/en-US/docs/DOM/element.dispatchEvent

例子：

function simulateClick() {
  var evt = document.createEvent("MouseEvents");
  evt.initMouseEvent("click", true, true, window,
    0, 0, 0, 0, 0, false, false, false, false, 0, null);
  var cb = document.getElementById("checkbox"); 
  var canceled = !cb.dispatchEvent(evt);
  if(canceled) {
    // A handler called preventDefault
    alert("canceled");
  } else {
    // None of the handlers called preventDefault
    alert("not canceled");
  }
}

1. 创建事件

https://developer.mozilla.org/en-US/docs/DOM/document.createEvent

创建一个指定类型的事件。

语法：

var event = document.createEvent(type);

• event is the created Event object.
• type is a string that represents the type of event to be created. Possible event types include "UIEvents", "MouseEvents", "MutationEvents", and "HTMLEvents". See Notes section for details.

2. 根据不同的事件类型调用不同的初始化事件函数：

Event Module	Event type to pass to createEvent	Method to be used to initialize the event
DOM Level 2 Events
User Interface event module	"UIEvents"	event.initUIEvent
Mouse event module	"MouseEvents"	event.initMouseEvent
Mutation event module	"MutationEvents"	event.initMutationEvent
HTML event module	"HTMLEvents"	event.initEvent

3. 事件派发

bool = element.dispatchEvent(event)

• element is the target of the event.
• event is an event object to be dispatched.
• The return value is false if at least one of the event handlers which handled this event called preventDefault. Otherwise it returns true.

例子： https://developer.mozilla.org/samples/domref/dispatchEvent.html