Validate Numeric Only

1. Paste this code into an external JavaScript file named: validNum.js
   
   CODE
   // calculate the ASCII code of the given character
   function CalcKeyCode(aChar) {
     var character = aChar.substring(0,1);
     var code = aChar.charCodeAt(0);
     return code;
   }
   
   function checkNumber(val) {
     var strPass = val.value;
     var strLength = strPass.length;
     var lchar = val.value.charAt((strLength) - 1);
     var cCode = CalcKeyCode(lchar);
   
     /* Check if the keyed in character is a number
        do you want alphabetic UPPERCASE only ?
        or lower case only just check their respective
        codes and replace the 48 and 57 */
   
     if (cCode < 48 || cCode > 57 ) {
       var myNumber = val.value.substring(0, (strLength) - 1);
       val.value = myNumber;
     }
     return false;
   }
2. Paste this code into the HEAD section of your HTML document. You may need to change the path of the file.
   
   CODE
   <script type="text/javascript" src="validNum.js"></script>
3. Paste this code into the BODY section of your HTML document
   
   CODE
   <form name="myForm" method="post" action="#">
     Enter an integer here: <input name="txtNumber" type="text"
       id="txtNumber" onKeyUp="java script:checkNumber(myForm.txtNumber);">
   </form>
   

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