More info: http://catnip.fyi/posts/foundry-p1/
Foundryvtt (https://foundryvtt) < 0.8.0 deobfuscator. other javascript-obfuscator (https://www.npmjs.com/package/javascript-obfuscator) projects prolly work as well.
npm start <path to foundry dist directory>
dist directory is usually resources/app/dist from the foundry base directory.
Foundryvtt is using the npm package javascript-obfuscator so this deobfuscator should be able to deobfuscate other projects with a simmilar configuration. You can also feel free to use this project as a template for you own deobfuscator. Take a look at devisit.ts, thats where you overwrite the javascript syntax nodes.