Amber is a subset of Smalltalk running in a web browser. As opposed to modern Smalltalk dialects, it has no support for traits. It features a compiler that converts Smalltalk code to Javascript, and allows integrating existing Javascript code. Amber, also provides an IDE implemented in itself. However, it has many limitations such as no hot-swap of code, a limited debugger, and no refactoring. (See Test-Driven Development for Generated Portable Javascript Apps, p. 8)
From smalltalk to javascript and back. github 
https://lolg.it/amber/amber – Amber is an implementation of the Smalltalk language that runs on top of the JavaScript runtime. It is designed to make client-side development faster and easier.
https://amber-lang.net/ – project page
# Overview
Amber is written in itself, including the parser and compiler. Amber compiles into efficient JavaScript, mapping one-to-one with the equivalent JavaScript. There is no interpretation at runtime.
Pharo Smalltalk is considered as the reference implementation.