js中获取键盘事件及禁止退格键Backspace处理

<script type="text/javascript" language=JavaScript charset="UTF-8">
        document.onkeydown=function(event){
              var e = event || window.event || arguments.callee.caller.arguments[0];
              if(e && e.keyCode==27){ // 按 Esc 
                 //要做的事情
                }
              if(e && e.keyCode==113){ // 按 F2 
                   //要做的事情
                 }            
              if(e && e.keyCode==13){ // enter 键
                  //要做的事情
            }
         }; 
14 </script>
15 只要你定义了这些键的动作，你在浏览器里按下这些键就会响应，兼容目前所有浏览器。

  js 里面的键盘事件经常用到，所以收集了键盘事件对应的键码来分享下：
   keyCode 8 = BackSpace BackSpace
   keyCode 9 = Tab Tab
   keyCode 12 = Clear
   keyCode 13 = Enter
   keyCode 16 = Shift_L
   keyCode 17 = Control_L
   keyCode 18 = Alt_L
   keyCode 19 = Pause
   keyCode 20 = Caps_Lock
   keyCode 27 = Escape Escape
   keyCode 32 = space
   keyCode 33 = Prior
   keyCode 34 = Next
   keyCode 35 = End
   keyCode 36 = Home
   keyCode 37 = Left
   keyCode 38 = Up
   keyCode 39 = Right
   keyCode 40 = Down
   keyCode 41 = Select
   keyCode 42 = Print
   keyCode 43 = Execute
   keyCode 45 = Insert
   keyCode 46 = Delete
   keyCode 47 = Help
   keyCode 48 = 0 equal braceright
   keyCode 49 = 1 exclam onesuperior
   keyCode 50 = 2 quotedbl twosuperior
   keyCode 51 = 3 section threesuperior
   keyCode 52 = 4 dollar
   keyCode 53 = 5 percent
  keyCode 54 = 6 ampersand
   keyCode 55 = 7 slash braceleft
   keyCode 56 = 8 parenleft bracketleft
   keyCode 57 = 9 parenright bracketright
   keyCode 65 = a A
   keyCode 66 = b B
   keyCode 67 = c C
   keyCode 68 = d D
   keyCode 69 = e E EuroSign
   keyCode 70 = f F
   keyCode 71 = g G
   keyCode 72 = h H
   keyCode 73 = i I
   keyCode 74 = j J
   keyCode 75 = k K
   keyCode 76 = l L
   keyCode 77 = m M mu
   keyCode 78 = n N
   keyCode 79 = o O
   keyCode 80 = p P
   keyCode 81 = q Q at
   keyCode 82 = r R
   keyCode 83 = s S
   keyCode 84 = t T
   keyCode 85 = u U
   keyCode 86 = v V
   keyCode 87 = w W
   keyCode 88 = x X
   keyCode 89 = y Y
   keyCode 90 = z Z
   keyCode 96 = KP_0 KP_0
   keyCode 97 = KP_1 KP_1
   keyCode 98 = KP_2 KP_2
   keyCode 99 = KP_3 KP_3
   keyCode 100 = KP_4 KP_4
   keyCode 101 = KP_5 KP_5
   keyCode 102 = KP_6 KP_6
   keyCode 103 = KP_7 KP_7
   keyCode 104 = KP_8 KP_8
   keyCode 105 = KP_9 KP_9
   keyCode 106 = KP_Multiply KP_Multiply
   keyCode 107 = KP_Add KP_Add
   keyCode 108 = KP_Separator KP_Separator
   keyCode 109 = KP_Subtract KP_Subtract
   keyCode 110 = KP_Decimal KP_Decimal
   keyCode 111 = KP_Divide KP_Divide
   keyCode 112 = F1
   keyCode 113 = F2
   keyCode 114 = F3
   keyCode 115 = F4
   keyCode 116 = F5
   keyCode 117 = F6
   keyCode 118 = F7
   keyCode 119 = F8
   keyCode 120 = F9
   keyCode 121 = F10
   keyCode 122 = F11
   keyCode 123 = F12
   keyCode 124 = F13
   keyCode 125 = F14
   keyCode 126 = F15
   keyCode 127 = F16
   keyCode 128 = F17
   keyCode 129 = F18
   keyCode 130 = F19
   keyCode 131 = F20
   keyCode 132 = F21
  keyCode 133 = F22
   keyCode 134 = F23
   keyCode 135 = F24
   keyCode 136 = Num_Lock
   keyCode 137 = Scroll_Lock
   keyCode 187 = acute grave
   keyCode 188 = comma semicolon
   keyCode 189 = minus underscore
   keyCode 190 = period colon
   keyCode 192 = numbersign apostrophe
   keyCode 210 = plusminus hyphen macron
   keyCode 211 =
   keyCode 212 = copyright registered
   keyCode 213 = guillemotleft guillemotright
   keyCode 214 = masculine ordfeminine
   keyCode 215 = ae AE
   keyCode 216 = cent yen
   keyCode 217 = questiondown exclamdown
   keyCode 218 = onequarter onehalf threequarters
   keyCode 220 = less greater bar
   keyCode 221 = plus asterisk asciitilde
   keyCode 227 = multiply division
   keyCode 228 = acircumflex Acircumflex
   keyCode 229 = ecircumflex Ecircumflex
   keyCode 230 = icircumflex Icircumflex
   keyCode 231 = ocircumflex Ocircumflex
   keyCode 232 = ucircumflex Ucircumflex
   keyCode 233 = ntilde Ntilde
   keyCode 234 = yacute Yacute
   keyCode 235 = oslash Ooblique
   keyCode 236 = aring Aring
   keyCode 237 = ccedilla Ccedilla
   keyCode 238 = thorn THORN
   keyCode 239 = eth ETH
   keyCode 240 = diaeresis cedilla currency
   keyCode 241 = agrave Agrave atilde Atilde
   keyCode 242 = egrave Egrave
   keyCode 243 = igrave Igrave
   keyCode 244 = ograve Ograve otilde Otilde
   keyCode 245 = ugrave Ugrave
   keyCode 246 = adiaeresis Adiaeresis
   keyCode 247 = ediaeresis Ediaeresis
   keyCode 248 = idiaeresis Idiaeresis
   keyCode 249 = odiaeresis Odiaeresis
   keyCode 250 = udiaeresis Udiaeresis
   keyCode 251 = ssharp question backslash
   keyCode 252 = asciicircum degree
   keyCode 253 = 3 sterling
   keyCode 254 = Mode_switch
使用event对象的keyCode属性判断输入的键值
eg：if(event.keyCode==13)alert(“enter!”);
 键值对应表
 A　　0X65 　U 　　0X85
 B　　0X66　 V　　 0X86
 C　　0X67　 W　　 0X87
 D　　0X68　 X 　　0X88
 E　　0X69　 Y　　 0X89
 F　　0X70　 Z　　 0X90
 G　　0X71　 0　　 0X48
 H　　0X72　 1　　 0X49
 I　　0X73　 2　　 0X50
 J　　0X74　 3 　　0X51
 K　　0X75　 4 　　0X52
 L　　0X76　 5 　　0X53
 M　　0X77　 6　　 0X54
 N　　0X78 　7 　　0X55
 O　　0X79 　8 　　0X56
 P　　0X80 　9 　　0X57
 Q　　0X81　ESC　　0X1B
 R　　0X82　CTRL 　0X11
 S　　0X83　SHIFT　0X10
 T　　0X84　ENTER　0XD
 如果要使用组合键，则可以判断是否同时按下了这几个键，比如ctrl键、shift键以及alt键的组合使用就可以判断是否多按下了ctrl键、shift键以及alt键

============================

js 屏蔽Backspace事件

function document.onkeydown() {
if (event.keyCode == 8) { 
if (document.activeElement.type == "text") {
if (document.activeElement.readOnly == false)
return true; 
} 
return false;
}
}