OnKeyPress and OnBlur Event in JS

////---- Function allow Numeric value only
function isNumberOnly(evt){   
    var charCode = (evt.which) ? evt.which : evt.keyCode
    if (charCode > 31 && ///Special Char ASCII (31~47)
       (charCode < 48 || charCode > 57)) ///0-9 Number ASCII (48~57)
        return false;
    return true;
}

OR

function isNumberOnly(evt){   
    var charCode = (evt.which) ? evt.which : evt.keyCode
    if (charCode > 31 &&  ///Special Char ASCII (31~47)
       (charCode < 48 || charCode > 57)) ///0-9 Number ASCII (48~57)
        return false;
    return true;

}


function fnValidateNumber()
{
var strNo, regexpNum;
strNo = document.getElementById("fldIdMyTxtBox").value;
regexpNum = /^[0-9]*$/;

if(!strNo== "")
{
if(!strNo.match(regexpNum))
{
document.getElementById('fldIdMyTxtBox').className = 'input-error';
document.getElementById('fldIdMyTxtBoxInline').style.display = "block";
document.getElementById('fldIdMyTxtBoxInline').innerHTML = 'Field cannot have alphabets or special characters.';
return false;
}
else
{
document.getElementById('fldIdMyTxtBox').className = 'objinputtext';
document.getElementById('fldIdMyTxtBoxInline').style.display = "none";
document.getElementById('fldIdMyTxtBoxInline').innerHTML = '';
return true;
}
}

}


HTML:
<input type="text" id="fldIdMyTxtBox" name="MyTxtBox" onkeypress="return isNumberOnly(event);" onBlur="fnValidateNumber();" />




////---- Function allow Alphabet, Space, Under Score and Number value only
function isAlphabetNumberOnly(evt){   
    var charCode = (evt.which) ? evt.which : evt.keyCode;
    var retVal = ((charCode &gt;= 48 &amp;&amp; charCode &lt;= 57) || ///0-9 Number ASCII (48~57)
          (charCode &gt;= 65 &amp;&amp; charCode &lt;= 90) || ///A~Z Upper Case Alphabet ASCII (65~90)
          (charCode &gt;= 97 &amp;&amp; charCode &lt;= 122) || ///a~z Lower Case Alphabet ASCII (97~122)
          (charCode == 32) ||  ///Space ASCII (32)
          (charCode == 95) ///UnderScore ASCII (95)
          );
if(retVal == false)
{
  return false;
}
else
{
  return true;
}
}

OR

function isAlphabetNumberOnly(evt){   
    var charCode = (evt.which) ? evt.which : evt.keyCode;
    var retVal = ((charCode >= 48 && charCode <= 57) ||  ///0-9 Number ASCII (48~57)
           (charCode >= 65 && charCode <= 90) ||  ///A~Z Upper Case Alphabet ASCII (65~90)
           (charCode >= 97 && charCode <= 122) || ///a~z Lower Case Alphabet ASCII (97~122)
           (charCode == 32) ||   ///Space ASCII (32)
           (charCode == 95)   ///UnderScore ASCII (95)
           );
if(retVal == false)
{
  return false;
}
else
{
  return true;
}
}

function fnValidateAlphaNumber()
{
var strUserRefNo, regexpNum;
strUserRefNo = document.getElementById("fldIdMyTxtBoxUserRef").value;
regexpNum = /^[A-Za-z0-9 _]*$/;

if(!strUserRefNo == "")
{
if(!strUserRefNo.match(regexpNum))
{
document.getElementById('fldIdMyTxtBoxUserRef').className = 'input-error';
document.getElementById('fldIdMyTxtBoxUserRefInline').style.display = "block";
document.getElementById('fldIdMyTxtBoxUserRefInline').innerHTML = 'Your reference cannot have special characters.';
return false;
}
else
{
document.getElementById('fldIdMyTxtBoxUserRef').className = 'objinputtext';
document.getElementById('fldIdMyTxtBoxUserRefInline').style.display = "none";
document.getElementById('fldIdMyTxtBoxUserRefInline').innerHTML = '';
return true;
}
}

}

HTML:
<input type="text" id="fldIdMyTxtBoxUserRef" name="MyTxtBoxUserRef" onkeypress="return isAlphabetNumberOnly(event);" onBlur="fnValidateAlphaNumber();" />



ON Submit Button JS:

var validateNo = fnValidateNumber();
if(validateNo == false)
{
document.getElementById('fldIdMyTxtBox').className = 'input-error';
document.getElementById('fldIdMyTxtBoxInline').style.display = "block";
return false;
}
else
{
document.getElementById('fldIdMyTxtBox').className = 'objinputtext';
document.getElementById('fldIdMyTxtBoxInline').style.display = "none";
document.getElementById('fldIdMyTxtBoxInline').innerHTML = '';

}


var validateUsrRefNo = fnValidateAlphaNumber();
if(validateUsrRefNo == false)
{
document.getElementById('fldIdMyTxtBoxUserRef').className = 'input-error';
document.getElementById('fldIdMyTxtBoxUserRefInline').style.display = "block";
return false;
}
else
{
document.getElementById('fldIdMyTxtBoxUserRef').className = 'objinputtext';
document.getElementById('fldIdMyTxtBoxUserRefInline').style.display = "none";
document.getElementById('fldIdMyTxtBoxUserRefInline').innerHTML = '';
}