Registry / testing / eslint-plugin-immutable

eslint-plugin-immutable

library1.0.0jsnpmunverified

This ESLint plugin enforces immutability in JavaScript by providing three rules: no-let (forces use of const instead of let/var), no-this (disallows this in favor of functional components), and no-mutation (prevents assignment to member expressions, blocking object mutation even with const). Version 1.0.0 is stable. It integrates with Redux+React workflows, using Babel's object-rest-spread plugin for immutable updates. Differentiates from general eslint rules by specifically targeting Redux/React patterns, with no runtime cost compared to Object.freeze().

testing

npm install eslint-plugin-immutable

github ↗package ↗

INSTALL

IMPORT

SIG · ESLINT-PLUGIN-IMMU

eslint-plugin-immutable

testingjavascriptv1.0.0

Install

—

Import

—

Disk

—

Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

no-let

✓ /* ESLint config: */ "rules": { "immutable/no-let": 2 }

✗ "rules": { "no-let": 2 }

Must prefix with 'immutable/' in ESLint rules.

no-this

✓ /* ESLint config: */ "rules": { "immutable/no-this": 2 }

✗ "rules": { "no-this": 2 }

Must prefix with 'immutable/' in ESLint rules.

no-mutation

✓ /* ESLint config: */ "rules": { "immutable/no-mutation": 2 }

✗ "rules": { "no-mutation": 2 }

Must prefix with 'immutable/' in ESLint rules.

Shows installation, configuration, and examples of code that violates each rule.

// Install npm install eslint-plugin-immutable --save-dev // .eslintrc.json { "plugins": ["immutable"], "rules": { "immutable/no-let": 2, "immutable/no-this": 2, "immutable/no-mutation": 2 } } // Example file: index.js const add = (a, b) => a + b; // Works let x = 5; // Error: Unexpected let or var, use const class MyComponent extends React.Component { // Error: no this allowed render() { return <div>{this.props.message}</div>; // Error: no this allowed } } const point = { x: 1 }; point.x = 2; // Error: No object mutation allowed

Debug

Known issues

gotchaDisabling 'no-this' rule may still allow 'this' in arrow functions if used in class contexts.

fix

Use only functional components and avoid classes entirely.

affects: >=1.0.0

gotchaThe 'no-mutation' rule does not prevent array mutations via methods like push, splice, or sort. It only blocks member expression assignment (e.g., obj.prop = value).

fix

Supplement with eslint-plugin-immutable's no-array-mutation rule or use array spread/immutable library.

affects: >=1.0.0

gotchaThe 'no-let' rule does not cover for-in loops where 'let' is implicit? Actually for-in with 'let' is caught, but for-of loops still require 'let' for iteration variable, which will be flagged. Use forEach or map instead.

fix

Replace for-loops with array methods like map, filter, reduce, or forEach.

affects: >=1.0.0

Errors

Common errors & fixes

ESLint: Unexpected let or var, use const. (immutable/no-let)

Using let or var declaration in code.

fix

Replace 'let' with 'const' or refactor to use array methods.

ESLint: No object mutation allowed. (immutable/no-mutation)

Assigning a value to a property of an object.

fix

Use object spread: const newObj = { ...oldObj, prop: newValue };

ESLint: No this allowed. (immutable/no-this)

Using 'this' in a React component class or other context.

fix

Convert to a stateless functional component using props parameter.

Upgrade

Version history

1.0.0latest on npm

Audit

Dependencies

eslintrequiredpeer dependency: requires ESLint to function as a plugin

Agent activity

4 hits · last 30 days

node

Resources

githubhttps://github.com/jhusain/eslint-plugin-immutable ↗

packagehttps://www.npmjs.com/package/eslint-plugin-immutable ↗