javascript ดักจับ key ที่พิมพ์ ตัวที่ 1 ให้กรอกเฉพาะ 1,2,Sตัวที่ 2 ให้กรอกเฉพาะ /ตัวที่ 3 ให้กรอก

<script language="javascript">

function checkID(id)
{
      if(document.form1.zipcode.value == ""){
		alert('ข้อความที่ต้องการ');
		document.form1.zipcode.focus();
		return false;
}
	else if(isNaN(document.form1.ชื่อtextbox.value)) {
		alert("ข้อความเช่น ต้องกรอกเป็นตัวเลขเท่านั้น") ; 
		document.form1.zipcode.focus() ;
		return false ;	

}  
    document.form1.submit();
}
</script>

//================================================
//  Function    : numericOnly
//  Description : allows user to enter only numeric values in textbox
//  Input       : intType
//
//  intType = 1 : used for numeric only values 0 to 9 only
//  intType = 2 : allows  '/' character usually intended for date text box "YYYY/MM/DD" type
//  intType = 3 : allows  '.' character usually intended for values with decimal
//  intType = 4 : allows  '-' character useally intended for zip or tel/fax
//  intType = 5 : allows  ':' character useally intended
//  intType = 6 : allows  '-' character useally intended for minus
//  intType = 7 : allows  '-','.' character  usually intended for values with decimal or minus
//================================================
function numericOnly(obj, evnt, intType) {
    var strVal;
    var _keycode;
    var _srcelement;
    
    if(window.event) {
        _keycode = 	window.event.keyCode;
        _srcelement = window.event.srcElement.value;
    }else {
        _keycode = 	evnt.which;
        _srcelement = obj.value;
    }
	
    if (_keycode < 48 || _keycode > 57)  // 0 to 9
    {
        if(_keycode == 13){ //[_keycode == 13 is enter button]
            return;
        }
        if (intType == 1){
			
            if(window.event) {
                window.event.keyCode = 0;
            }else {
                if( !(_keycode == 8 || _keycode == 0) ){
                    evnt.preventDefault();
                }
                return;
            }
        }
        else
        {
            if((intType == 6 || intType == 7) && _keycode == 45 || _keycode == 0) {
                strVal = _srcelement;
                if(strVal.indexOf("-", 0)!=-1){
                    if(window.event) {
                        window.event.keyCode = 0;
                    }else {
                        evnt.preventDefault();
                    }
                }
                return;
            }

            if (_srcelement == '')
            {
                if(window.event) {
                    window.event.keyCode = 0;
                }else {
                    evnt.preventDefault();
                }
                return;
            }
            if ((intType == 2 && _keycode  == 47)){ //  allows '/' character
                strVal = _srcelement;
            }
            else if ((intType == 3 || intType == 7) && _keycode  == 46 || _keycode == 0)
            {
                strVal = _srcelement;
                if(strVal.indexOf('.',0) != -1) {
                    if(window.event) {
                        window.event.keyCode = 0;
                    }else {
                        evnt.preventDefault();
                    }
                }
            }
            else if (intType == 4 && _keycode  == 45 || _keycode == 0)  //  allows '-' character
                return;
            else if (intType == 5 && _keycode  == 58 || _keycode == 0)  //  allows ':' character ACE Add
                return;
            else {
                if(window.event) {
                    window.event.keyCode = 0;
                }else {
                    if( !(_keycode == 8 || _keycode == 0) ){
                        evnt.preventDefault();
                    }
                    return;
                }
            }
        }
    }
}