js onkeypress与onkeydown 事件区别详细说明

onkeypress 和 onkeydown 是有区别，下面将讲解 onkeypress 与 onkeydown 事件的区别。
onkeypress 事件在用户按下并放开任何字母数字键时发生。但是系统按钮（例如：箭头键、功能键）无法得到识别。
onkeydown 事件在用户按下任何键盘键（包括系统按钮）时发生。
具体区别：
1. 一个放开一个没有放开，onkeydown 先于 onkeypress 发生。
2.onkeypress 无法系统按钮。
2.onkeydown 捕获的 keyCode 不区分字母大小，而 onkeypress 区分。

onkeypress是在用户按下并放开任何字母数字键时发生。系统按钮（例如，箭头键和功能键）无法得到识别。
onkeyup 是在用户放开任何先前按下的键盘键时发生。
onkeydown 是在用户按下任何键盘键（包括系统按钮，如箭头键和功能键）时发生。

onkeypress
As of Microsoft® Internet Explorer 4.0, the onkeypress event fires and can be canceled for the following keys:

Letters: A - Z (uppercase and lowercase)
Numerals: 0 - 9
Symbols: ! @ # $ % ^ & * ( ) _ - = < [ ] { } , . / ? \ | ' ` " ~
System: ESC, SPACEBAR, ENTER

onkeydown
As of Microsoft&reg; Internet Explorer 4.0, the onkeydown event fires for the following keys:

Editing: DELETE, INSERT
Function: F1 - F12
Letters: A - Z (uppercase and lowercase)
Navigation: HOME, END, LEFT ARROW, RIGHT ARROW, UP ARROW, DOWN ARROW
Numerals: 0 - 9
Symbols: ! @ # $ % ^ & * ( ) _ - = < [ ] { } , . / ? \ | ' ` " ~
System: ESC, SPACEBAR, SHIFT, TAB

As of Internet Explorer 5, the event also fires for the following keys:

Editing: BACKSPACE
Navigation: PAGE UP, PAGE DOWN
System: SHIFT TAB

As of Internet Explorer 5, this event can be canceled for the following keys and key combinations by specifying event.returnValue=false:

Editing: BACKSPACE, DELETE
Letters: A - Z (uppercase and lowercase)
Navigation: PAGE UP, PAGE DOWN, END, HOME, LEFT ARROW, RIGHT ARROW, UP ARROW, DOWN ARROW
Numerals: 0 - 9
Symbols: ! @ # $ % ^ & * ( ) _ - = < [ ] { } , . / ? \ | ' ` " ~
System: SPACEBAR, ESC, TAB, SHIFT TAB

You can cancel all keys that fire the onkeydown event in HTML Applications, including most accelerator keys, such as ALT F4.

In Internet Explorer 4.0, you cannot cancel the onkeydown event, but you can use the onkeypress event to cancel keyboard events.

两个一起按，可以这样：

if( window.event.shiftKey && event.keyCode==xx) 

function document_onpress() 
{ 

if(event.keyCode=='13') 
{ 
document.all.div_Line.style.pixelLeft=document.all.div_Line.style.pixelLeft 1; 
document.all.div_Q.style.pixelLeft=document.all.div_Q.style.pixelLeft 1; 
document.all.div_T.style.pixelLeft=document.all.div_T.style.pixelLeft 1; 

}