//isInteger.js
function isInteger(strString)
//boolean function to check string for valid integer value (non-negative)
{
var strValidChars = "0123456789";
var strChar;
var blnResult = true;

//  test strString consists of valid characters listed above
for (var i = 0; i < strString.length && blnResult == true; i++)
   {
   strChar = strString.charAt(i);
   if (strValidChars.indexOf(strChar) == -1)
      blnResult = false;
   }
return blnResult;
}