Add a trigger event to the JS-attachevent ()/addeventlistener () object.

JS addevent binding analysis:

Function addevent (ELEM, eventname, Handler ){
If (ELEM. addeventlistener ){
ELEM. addeventlistener (eventname, handler, usercapture );
} Else if (ELEM. attachevent ){
ELEM. attachevent ("On" + eventname, Handler );
}
}; Firefox-> addeventlistener, third parameter Usercapture Usercapture If it is true, the browser uses the capture (capture) method. If it is false, the bubbing (bubble) method is used. False is recommended. When an event of an object is triggered Program It may be a large string. It may be a call to a function or a call to another function at the same time.

Document. getelementbyid ("BTN"). onclick = Method1;
Document. getelementbyid ("BTN"). onclick = method2;
Document. getelementbyid ("BTN"). onclick = method3;
If this is the case, only medhot3 will be executed.

In (IE) Using attachevent,

VaR btn1obj = Document. getelementbyid ("btn1 ");

// Object. attachevent (event, function );

Btn1obj. attachevent ("onclick", Method1 );

Btn1obj. attachevent ("onclick", method2 );

Btn1obj. attachevent ("onclick", method3 );

The execution sequence is method3-> method2-> Method1

Addeventlistener must be used in the Mozilla Series

VaR btn1obj = Document. getelementbyid ("btn1 ");

// Element. addeventlistener (type, listener, usecapture );

Btn1obj. addeventlistener ("click", Method1, false );

Btn1obj. addeventlistener ("click", method2, false );

Btn1obj. addeventlistener ("click", method3, false );

The execution sequence is Method1-> method2-> method3

Look at gmail'sCode

VaR Ka = navigator. useragent. tolowercase ();

VaR RT = ka. indexof ("Opera ")! =-1;

VaR r = ka. indexof ("MSIE ")! =-1 & (document. All &&! RT );

Function ZL (a, B, c) {If (r) {. attachevent ("On" + B, c)} else {. addeventlistener (B, c, false )}}