Besides notifications, it supports alerts + confirmations and doesn’t require any other JS libraries to run.
The positions of the messages, their auto-expire duration and whether they can be controlled via keyboard or not can all be configured.
Each message type (except notifications) has callbacks for a customized interaction and the look/feel of messages can be completely styled.
This library was extracted from the code of DHTMLX suite. jsMessages library can be used under terms of MIT license (basically free).