This is a function normally found in the C language. However it is useful to script developers as well, and may be available in some implementations as an extension to the ECMA standard functionality.

This function tests to see if a character is a letter or a number. A letter is any character for which the isAlpha() function returns true. Likewise a number is any character for which isDigit() returns true.

Strictly speaking, this function should be coded to be aware of locale specific issues. You may want to take the example simulation provided here and modify it to your own needs to support that. This is just a basic working example.

Example code:

   // Test for letters and digits

   function isAlnum(aChar)

   {

      return (isDigit(aChar) || isAlpha(aChar));

   }

   // Test for digits

   function isDigit(aChar)

   {

      myCharCode = aChar.charCodeAt(0);

   

      if((myCharCode > 47) && (myCharCode <  58))

      {

         return true;

      }

   

      return false;

   }

   // Test for letters (only good up to char 127)

   function isAlpha(aChar)

   {

      myCharCode = aChar.charCodeAt(0);

   

      if(((myCharCode > 64) && (myCharCode <  91)) ||

        ((myCharCode > 96) && (myCharCode < 123)))

      {

         return true;

      }

   

      return false;

   }