Today I implemented a smol lisp parser and interpreter for a project! I wrote in javascript but I was following this super clear python implementation http://kjetilvalle.com/posts/original-lisp.html
The parser is http://bananabanana.me/murilisp/baby-lisper.js
The interpreter (with extended functions) is http://bananabanana.me/murilisp/lisp.js
There is a single file version at http://bananabanana.me/murilisp/murilisp.html