eslint-plugin-chain-max-length

Enforce a maximum length on chained array method calls

eslint-plugin-chain-max-length helps you keep your JavaScript clean and efficient by warning against long chains like .map().filter().reduce() that create multiple intermediate arrays.

This plugin is designed to encourage the use of the new Iterator Helpers (.values(), .drop(), .take(), .toArray(), etc.) introduced in ES2024, which enable lazy pipelines and avoid unnecessary array creation.

Installation

npm install --save-dev eslint-plugin-chain-max-length

Configuration

Add the plugin to your eslint.config.js:

import chainMaxLengthPlugin from 'eslint-plugin-chain-max-length';
import { defineConfig } from 'eslint/config';

export default defineConfig([
  {
    plugins: {
      chainMaxLengthPlugin,
    },
    rules: {
      'chainMaxLengthPlugin/chain-max-length': ['warn', 3],
    },
  },
]);

Rule: chain-max-length

• Type: suggestion
• Options: An integer (minimum 1) representing the maximum number of standard array methods allowed in a single chain.
• Checked methods:
  • map, filter, reduce, reduceRight, flat, flatMap, slice, concat, toSorted, toReversed, toSpliced.
• Exception: Chains starting with .values() and ending with .toArray() (lazy pipelines) are ignored.

Examples

Long chain (warns)

// Warning: 4 methods > limit of 3
[1, 2, 3]
  .map((x) => x + 1)
  .filter((x) => x > 2)
  .reduce((a, b) => a + b, 0)
  .sort()
  .slice(0, 5);

Using Iterator Helpers (no warning)

// Lazy pipeline: no intermediate arrays created
[1, 2, 3]
  .values() // returns an iterator
  .map((x) => x + 1)
  .filter((x) => x > 2)
  .drop(10)
  .take(10)
  .toArray(); // converts back to array