salesforceIdValidator.js

$(function () {
   $('#update-sf-id').click(function () {
      var answer = prompt(
         "Enter a 15 character Salesforce ID",
         $('#SalesForceID').val().substr(0, 15)
      );

      if (answer == '' || answer == null) {
         alert("Please enter a Salesforce ID");
      } else if (answer.length != 15) {
         alert("Salesforce ID's can only be 15 characters long");
      } else if (answer != null && answer.length == 15) {
         $('#SalesForceID').val(function () {
            var chunks = new Array();
            chunks[0] = answer.substr(0, 5);
            chunks[1] = answer.substr(5, 5);
            chunks[2] = answer.substr(10, 5);
            var bits = 0;
            var extra = '';

            for (i in chunks) {
               var chunk = chunks[i];
               bits = 0;
               for (j in chunk) {
                  if (chunk[j] < = 'Z' && chunk[j] >= 'A') {
                     bits += Math.pow(2, j);
                  };
               }

               if (bits < 26) {
                  extra += String.fromCharCode('A'.charCodeAt(0) + bits);
               } else {
                  extra += String.fromCharCode('0'.charCodeAt(0) + (bits - 26));
               }
            };
            return answer + extra;
         });
      }
   });
});