ESLint — The Pluggable JavaScript and TypeScript Linter

What it is

ESLint is the most widely used linter for JavaScript and TypeScript. It statically analyzes your code to find problems, enforce coding standards, and automatically fix many issues. Its plugin system supports React, Vue, Angular, Node.js, and virtually any JavaScript ecosystem through community rules.

ESLint targets every JavaScript and TypeScript developer. Whether you work solo or on a large team, ESLint catches bugs, prevents anti-patterns, and ensures code consistency before your code reaches review or production.

Why it saves time or tokens

ESLint catches bugs like unreachable code, unused variables, and type coercion issues before runtime. The auto-fix feature corrects many style and logic issues automatically. When AI assistants generate JavaScript code, running ESLint on the output validates correctness and style compliance without human review of every line, reducing the iteration tokens needed to get clean code.

How to use

1. Install ESLint: npm install -D eslint
2. Initialize config: npx eslint --init and choose your framework and style preferences
3. Run ESLint: npx eslint . --fix to lint and auto-fix your codebase

Example

// eslint.config.js (flat config format)
import js from '@eslint/js';
import tseslint from 'typescript-eslint';

export default [
  js.configs.recommended,
  ...tseslint.configs.recommended,
  {
    rules: {
      'no-unused-vars': 'error',
      'no-console': 'warn',
      'prefer-const': 'error',
      '@typescript-eslint/no-explicit-any': 'warn'
    }
  }
];

Related on TokRepo

• AI tools for coding — developer tools and linters on TokRepo
• Automation tools — CI and code quality automation

Common pitfalls

• ESLint 9 uses flat config (eslint.config.js) by default; legacy .eslintrc files require the ESLINT_USE_FLAT_CONFIG=false flag
• Combining ESLint style rules with Prettier causes conflicts; use eslint-config-prettier to disable overlapping rules
• Too many enabled rules overwhelm developers with warnings; start with a recommended config and add rules incrementally