This example randomly generates a password from a base word and numbers. The base word is selected depending on the credential store. The code would be contained in the Script field of an extension script named SamplePasswordGenerator:

var SamplePasswordGenerator = Class.create();

SamplePasswordGenerator.prototype = {

  category: 'password_reset.extension.password_generator', // DO NOT REMOVE THIS LINE!

  /**********

    * Returns an auto-generated string password.

    * This sample randomly generates 4 digits to add to the password.

    *

    * @param params.credentialStoreId The sys_id of the target password reset credential store to generate

    *   a password for (table: pwd_cred_store)

    * @return An auto-generated string password

    **********/

  process: function(params) {

  var basePassword;

  var gr = new GlideRecord('pwd_cred_store');

  gr.addQuery('name', 'Local ServiceNow Instance');

  gr.query();

  if (gr.next()) {

  if (params.credentialStoreId == gr.getValue('sys_id'))

  basePassword = "Password";

  else

  basePassword = "Dorwssap";

  }

  return this.generateSimple(basePassword);

  },

  generateSimple : function(base) {

      var pwd = base;

      var numbers = '0123456789';

      var length = 4;

      for (var i = 0, n = numbers.length; i < length; i++) {

              pwd += numbers.charAt(Math.floor(Math.random() * n) +1);                

      }

      return pwd;

  },

  type: 'SamplePasswordGenerator'

};

http://wiki.servicenow.com/index.php?title=Password_Reset_Extension_Script_Includes#Password_Generat...