Javascript special value text box input verification

<! -- Only numerical values are allowed. -->
< Public: attach event = " Onpaste " Onevent = " Checkpaste () "   / >
< Public: attach event = " Onkeypress " Onevent = " Checkinput () "   / >
< Public: attach event = " Onfocus " Onevent = " Getfocus () "   / >
< Public: attach event = " Onblur " Onevent = " Lostfocus () "   / >
< Script Language = " Javascript " >
Function Checkinput (){
VaR K = Event. keycode;
Switch (Element. classname ){
Case   " Integeronly " :
/*
Only numbers and decimal places are allowed. Otherwise, disableinput
13 is a response
*/
If (K <   48 | K >   57 ) && K ! =   13 ){
Disableinput ();
}
Break ;
Case   " Decimalonly " :
/*
Only numbers are allowed. Otherwise, disableinput
13 is a response
46 is the decimal point
*/
If (K <   48 | K >   57 ) && K ! =   13 && K ! =   46 ){
Disableinput ();
}
Break ;
Case   " Usercode " :
/*
Only English letters, underscores, and numbers are allowed. Otherwise, disableinput
13 is a response
46 is the decimal point
*/
If (K <   97 | K >   122 ) // Lowercase letters
&& (K <   65 | K >   90 ) // Uppercase letters
&& (K <   48 | K >   57 ) // Number
&& K ! =   13 ){ // Return row
Disableinput ();
}
Break ;
}
}
/*
* Events triggered during pasting
* The called filtrateinput is in resume. aspx.
* Abandoned
  */
Function Checkpaste (){
Return   False ;
Ctrlid = Element. ID;
SetTimeout ( " Filtrateinput (\" " + Ctrlid + " \") " , 1 );
}
Function Disableinput (){
If (Element. classname =   " Integeronly "
| Element. classname =   " Decimalonly "
| Element. classname =   " Usercode " )
Event. returnvalue =   False ;
}
Function Getfocus (){
If (Element. Type =   " Text "  
| Element. Type =   " Password "
| Element. Type =   " Textarea " )
{
If ( ! (Element. readonly )){
Element. style. backgroundcolor =   " # Dcf1fa " ;
}
}
}
Function Lostfocus (){
If (Element. Type =   " Text "  
| Element. Type =   " Password "
| Element. Type =   " Textarea " )
{
Element. style. backgroundcolor =   "" ;
}
}
< / SCRIPT>