Source: Core/createGuid.js

/*global define*/
define(function() {
    'use strict';

    /**
     * Creates a Globally unique identifier (GUID) string.  A GUID is 128 bits long, and can guarantee uniqueness across space and time.
     *
     * @exports createGuid
     *
     * @returns {String}
     *
     *
     * @example
     * this.guid = Cesium.createGuid();
     * 
     * @see {@link http://www.ietf.org/rfc/rfc4122.txt|RFC 4122 A Universally Unique IDentifier (UUID) URN Namespace}
     */
    function createGuid() {
        // http://stackoverflow.com/questions/105034/how-to-create-a-guid-uuid-in-javascript
        return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c) {
            var r = Math.random() * 16 | 0;
            var v = c === 'x' ? r : (r & 0x3 | 0x8);
            return v.toString(16);
        });
    }

    return createGuid;
});