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An eslint config which reduces JS to a pure functional language
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.eslintrc Make it so. Aug 23, 2016
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index.js Disallow rest arguments in functions. Aug 31, 2016
package.json Support eslint 4 Jul 28, 2017


This project has never been seriously maintained, and you should be using eslint-plugin-fp directly instead.


This is an ESLint configuration which aims to restrict you to a subset of JavaScript which would be as close to an idealised pure functional language as possible. The idea is to see if it's possible to banish all the Bad Parts (well, except for the single numeric type being IEEE 754 floating point) and leave a language without the design flaws which have plagued JS from the start, and which aren't easy to design out of the language without becoming a subset of itself.

Please note that this rule set is meant for use only with ES6 or higher (and the ES7 object rest spread proposal helps a lot).


  • no this and no classes
  • no null and undefined (implying that all functions must return)
  • no mutation of any kind
  • no variable reassignment
  • no statements, only expressions (including no if)
  • no CommonJS or AMD, only ES6 modules

This is all based on three ESLint plugins, which you'll have to install to use these presets:


Just install this package somewhere your eslint can find it (npm install -g eslint-config-cleanjs if your eslint is installed with -g too), along with the three above mentioned plugins (npm install -g eslint-plugin-better eslint-plugin-fp eslint-plugin-import), and put this in your .eslintrc or wherever you keep your project's eslint config:

  "extends": "cleanjs"