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) {
    const r = (Math.random() * 16) | 0;
    const v = c === "x" ? r : (r & 0x3) | 0x8;
    return v.toString(16);
  });
}
Creates a Globally unique identifier (GUID) string.  A GUID is 128 bits long, and can guarantee uniqueness across space and time.

@function

@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}