SqueakJS is a Virtual Machine
for the Squeak dialect of Smalltalk, written in pure JavaScript by Bert Freudenberg.
Above is a stripped-down version of Squeak 2.2, which was released in 1998.
Modern Squeak versions are much more advanced, but more demanding, too. You can try
them on the SqueakJS launcher page.
Also, you may want to try the Lively SqueakJS Debugger.