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Getting Started

Install the plugin:

npm install --save-dev eslint-plugin-immutable-2 typescript

Enable one preset in your Flat Config:

import immutable from "eslint-plugin-immutable-2";

export default [
    immutable.configs.recommended,
];

recommended is the low-friction default preset. It works out of the box with the bundled parser wiring, and it gains additional semantic precision when you enable typed parser services for rules such as immutable-data. Move to immutable when you want no-let, readonly typing, and the warning-level no-method-signature rule in your baseline.

Alternative: manual scoped setup​

If you prefer to apply plugin rules inside your own file-scoped config object, spread the preset rules manually.

import tsParser from "@typescript-eslint/parser";
import immutable from "eslint-plugin-immutable-2";

export default [
    {
        files: ["**/*.{ts,tsx,mts,cts}"],
        languageOptions: {
            parser: tsParser,
            parserOptions: {
                ecmaVersion: "latest",
                // Enable when you want checker-backed precision.
                // projectService: true,
                sourceType: "module",
            },
        },
        plugins: {
            immutable,
        },
        rules: {
            ...immutable.configs.recommended.rules,
        },
    },
];

Use this pattern when you only extend rules and want full control over parser setup per scope.

  1. Start with recommended.
  2. Move to immutable when the team is ready for broader declaration and readonly typing discipline.
  3. Fix violations in small batches.
  4. Move to functional-lite for structural functional constraints such as loop and conditional restrictions.
  5. Move to functional once the team is ready for stricter statement, exception, and this bans.
  6. Use all when you want every immutable rule enabled.

Need a subset instead of a full preset?​

  • immutable.configs.immutable
  • immutable.configs["functional-lite"]
  • immutable.configs.functional

See the Presets section in this sidebar for details and examples.