Layer Browser engines contain a JS engine.
JS engine Chrome, Chromium, Edge: V8 written in C++ Safari: JavaScriptCore FireFox: SpiderMoney IE: Chakra Browser engine a.k.a layout engine, rendering engine.
Browser Browser engine Chrome Blink. Written in C++, V8 inside Safari Blink. Written in C++, V8 inside Edge Blink. Written in C++, V8 inside Opera Blink. Written in C++, V8 inside Safari Webkit Firefox Gecko Node.js stack https://medium.com/@chathuranga94/nodejs-architecture-concurrency-model-f71da5f53d1d
Top layer: Node.js libraries, written in JS Middle layer: Node.