Setting up ESLint + Prettier + Husky + lint-staged in a TypeScript repo

A complete, repeatable recipe for adding automated code quality to a Node/TypeScript project. By the end, every commit will be auto-formatted and lint-checked before it can land in your repo.

This guide assumes you have never set this up before. Read it once, follow the steps, and you’ll have a working setup. Bookmark it for the next repo.

1. Why are we doing this?

When several people work on a codebase, two problems show up quickly:

Style drift — one dev uses tabs, another uses 2-space indent, a third uses 4-space. PRs become a mess of formatting noise.
Quality drift — unused variables, accidental any types, let where const would do, missing returns. Each one is small; together they rot the codebase.

We solve both with four tools, each with a single job:

Tool	Job	Runs when
ESLint	Catches code-quality bugs (unused vars, `prefer-const`, type misuses)	On demand + pre-commit
Prettier	Auto-formats code so style is mechanical, not debated	On demand + pre-commit
Husky	Lets us hook into Git events (e.g. “before commit, run X”)	Every `git commit`
lint-staged	Runs tools only on the files you’re actually committing (fast)	Inside the husky hook

The flow we’re building:

git commit
   │
   ▼
husky pre-commit hook fires
   │
   ▼
lint-staged finds your staged files
   │
   ▼
runs prettier --write   (auto-format)
runs eslint --fix       (auto-fix safe issues; fail on the rest)
   │
   ▼
if everything passes → commit succeeds
if anything fails    → commit blocked, you fix it, retry

2. Prerequisites

Node.js 18+ and npm
A git repository (git init if you haven’t)
An existing package.json (npm init -y if you haven’t)
TypeScript already configured (the recipe also works for plain JS — skip the TS-specific bits)

3. Install ESLint (modern flat config, ESLint v9+)

ESLint v9 uses a new “flat config” format (eslint.config.mts / .js / .mjs). Older repos may have .eslintrc.json — that’s the legacy format. We use the new one because the official getting-started guide does.

Install

npm init @eslint/config@latest

This is an interactive installer. Answer:

How would you like to use ESLint? → “To check syntax, find problems”
What type of modules? → “JavaScript modules (import/export)”
Which framework? → “None of these” (or React/Vue if applicable)
Does your project use TypeScript? → Yes
Where does your code run? → Node (and Browser if applicable)
Install now? → Yes

It creates eslint.config.mts and adds dev dependencies: eslint, @eslint/js, globals, typescript-eslint.

Add npm scripts

In package.json, under "scripts":

"lint": "eslint .",
"lint:fix": "eslint . --fix"

Sanity check the generated config

Here’s what a correct minimal config looks like:

import js from "@eslint/js";
import globals from "globals";
import tseslint from "typescript-eslint";
import { defineConfig } from "eslint/config";
 
export default defineConfig([
    // 1) Global ignores — must be its own object with ONLY `ignores`.
    //    If you put `ignores` inside another config block, it only filters that block.
    { ignores: ["node_modules/**", "dist/**", "build/**", "test/**"] },
 
    // 2) Main config block
    {
        files: ["**/*.{js,mjs,cjs,ts,mts,cts}"],
        plugins: { js },
        extends: ["js/recommended"],
        languageOptions: {
            // Globals must be nested under `languageOptions.globals`.
            // A common mistake is spreading them directly into `languageOptions`.
            globals: { ...globals.node, ...globals.jest },
        },
        rules: {
            // Tweak rules to taste. Off / warn / error.
            "@typescript-eslint/no-explicit-any": "off",
        },
    },
 
    // 3) TypeScript recommended rules
    tseslint.configs.recommended,
]);

Verify

npm run lint

You’ll likely see lots of errors on existing code — that’s normal. We’ll deal with them in §7.

4. Install Prettier and integrate with ESLint

Prettier and ESLint overlap on formatting rules (indentation, quotes, semicolons). If both try to enforce style, they fight. The clean separation:

Prettier owns formatting (how code looks)
ESLint owns code quality (what code does)

Three packages do this:

Package	Purpose
`prettier`	The actual formatter
`eslint-config-prettier`	Disables every ESLint rule that conflicts with Prettier
`eslint-plugin-prettier`	Runs Prettier as an ESLint rule so violations show up in `npm run lint`

Install

npm install --save-dev prettier eslint-config-prettier eslint-plugin-prettier

Configure Prettier — `.prettierrc.json`

Create at repo root:

{
    "printWidth": 120,
    "tabWidth": 4,
    "useTabs": false,
    "semi": true,
    "singleQuote": false,
    "trailingComma": "es5",
    "bracketSpacing": true,
    "arrowParens": "always",
    "endOfLine": "lf"
}

These match the dominant style of this repo (4-space indent, double quotes, semicolons, 120-char lines). Adjust for yours — the important thing is that everyone agrees and it’s enforced by tooling, not humans.

Tell Prettier what to skip — `.prettierignore`

node_modules
dist
build
test
package-lock.json
*.md

Wire Prettier into ESLint — update `eslint.config.mts`

import js from "@eslint/js";
import globals from "globals";
import tseslint from "typescript-eslint";
import prettierPlugin from "eslint-plugin-prettier";
import prettierConfig from "eslint-config-prettier";
import { defineConfig } from "eslint/config";
 
export default defineConfig([
    { ignores: ["node_modules/**", "dist/**", "build/**", "test/**"] },
    {
        files: ["**/*.{js,mjs,cjs,ts,mts,cts}"],
        plugins: { js },
        extends: ["js/recommended"],
        languageOptions: {
            globals: { ...globals.node, ...globals.jest },
        },
        rules: {
            "@typescript-eslint/no-explicit-any": "off",
        },
    },
    tseslint.configs.recommended,
 
    // Order matters! prettierConfig must come AFTER tseslint so it can disable
    // any conflicting rules tseslint enabled.
    prettierConfig,
 
    // Then enable the prettier-as-a-rule plugin so violations show up in lint.
    {
        files: ["**/*.{js,mjs,cjs,ts,mts,cts}"],
        plugins: { prettier: prettierPlugin },
        rules: {
            "prettier/prettier": "error",
        },
    },
]);

Why the order matters: prettierConfig turns off ESLint’s stylistic rules. If you put it before tseslint.configs.recommended, the typescript rules might re-enable some of them. Prettier-config goes last among the rule blocks.

Add format scripts

In package.json "scripts":

"format": "prettier --write \"**/*.{ts,mts,cts,js,mjs,cjs,json}\"",
"format:check": "prettier --check \"**/*.{ts,mts,cts,js,mjs,cjs,json}\""

Verify

npm run format:check    # should report which files need formatting
npm run lint            # prettier violations now show up here too

5. Install Husky (Git hooks)

Husky lets you run scripts on Git events. We only care about pre-commit here.

Install

npm install --save-dev husky
npx husky init

husky init does three things:

Creates .husky/ directory with a sample pre-commit hook
Adds "prepare": "husky" to package.json scripts
Sets git config core.hooksPath .husky/_ so Git looks in this folder for hooks

The prepare script is important — it re-runs husky automatically after npm install, so a teammate who clones your repo gets the hooks set up without doing anything special.

Verify it’s wired up

git config core.hooksPath
# should print: .husky/_

If it prints nothing or a different path, run npx husky init again.

6. Install lint-staged and wire everything together

lint-staged runs commands only on staged files (the ones in git add). Without it, every commit would re-lint your entire codebase — slow and pointless.

Install

npm install --save-dev lint-staged

Configure — add to `package.json` (top level, NOT under `scripts`)

"lint-staged": {
    "*.{ts,mts,cts,js,mjs,cjs}": [
        "prettier --write",
        "eslint --fix"
    ],
    "*.json": "prettier --write"
}

Things to know:

An array means run in order. Prettier first (formats), then ESLint (catches quality issues on the now-clean code).
Use the top level of package.json, not nested inside "scripts".

Wire husky’s pre-commit hook to call lint-staged

Edit .husky/pre-commit so it contains exactly:

npx lint-staged

Verify the full pipeline

# 1. Make a deliberately ugly change to a TS file (bad indent, missing semi, etc.)
# 2. Stage it:
git add path/to/file.ts
 
# 3. Try to commit:
git commit -m "test"
 
# What should happen:
#   - lint-staged runs prettier --write (file gets reformatted, re-staged)
#   - lint-staged runs eslint --fix (auto-fixes safe issues)
#   - if any unfixable error remains → commit blocked
#   - otherwise → commit succeeds with the cleaned-up file

7. What to do about the existing mess

The first time you turn this on in an established repo, npm run lint will explode with hundreds of errors. Don’t panic — they were always there, you just couldn’t see them.

You have two options:

Option A — clean baseline (recommended)

Format and auto-fix everything in one pass, commit the result, then move on.

npm run format        # reformats everything per .prettierrc.json
npm run lint:fix      # auto-fixes safe ESLint issues (prefer-const, etc.)
npm run lint          # shows what's left

Manually fix the rest, or downgrade specific noisy rules to "warn" for now and tighten them later. Commit as one big “lint baseline” PR — reviewers can skim it because the diff is mechanical.

Option B — soft baseline

Downgrade noisy rules to "warn" in eslint.config.mts. New code gets held to the standard via lint-staged (because eslint --fix only touches staged files), and existing legacy code stays as-is.

Either way, the pre-commit hook only checks files you’re staging, so legacy errors never block your day-to-day commits.

8. Will this break my build or deploy?

No. Lint and build are independent pipelines:

Build (tsup, tsc, webpack, etc.) cares about type and syntax correctness. It does not run ESLint.
Deploy (cdk deploy, serverless, etc.) runs the build artifact. It does not run ESLint.
Pre-commit hook (lint-staged) only runs on git commit and only on staged files.

The only ways lint can block you:

You explicitly add npm run lint to your build/CI pipeline (you should, eventually — see §10).
You stage a file with errors and try to commit it.

9. Final file checklist

After all the steps, your repo should have:

.husky/
    pre-commit              # contains: npx lint-staged
.prettierrc.json            # Prettier config
.prettierignore             # Prettier ignore list
eslint.config.mts           # ESLint config (flat config, v9+)
package.json                # has scripts + lint-staged + devDependencies

And in package.json:

{
    "scripts": {
        "lint": "eslint .",
        "lint:fix": "eslint . --fix",
        "format": "prettier --write \"**/*.{ts,mts,cts,js,mjs,cjs,json}\"",
        "format:check": "prettier --check \"**/*.{ts,mts,cts,js,mjs,cjs,json}\"",
        "prepare": "husky"
    },
    "lint-staged": {
        "*.{ts,mts,cts,js,mjs,cjs}": [
            "prettier --write",
            "eslint --fix"
        ],
        "*.json": "prettier --write"
    },
    "devDependencies": {
        "@eslint/js": "...",
        "eslint": "...",
        "eslint-config-prettier": "...",
        "eslint-plugin-prettier": "...",
        "globals": "...",
        "husky": "...",
        "lint-staged": "...",
        "prettier": "...",
        "typescript-eslint": "..."
    }
}

12. Recap — replicating this in a new repo

A condensed sequence to copy/paste:

# 1. ESLint
npm init @eslint/config@latest        # follow prompts
 
# 2. Prettier
npm install --save-dev prettier eslint-config-prettier eslint-plugin-prettier
# create .prettierrc.json + .prettierignore (copy from §4)
# update eslint.config.mts to add prettierConfig + prettier plugin (copy from §4)
 
# 3. Husky
npm install --save-dev husky
npx husky init
 
# 4. lint-staged
npm install --save-dev lint-staged
# add lint-staged config to package.json (copy from §6)
# replace .husky/pre-commit contents with: npx lint-staged
 
# 5. Add npm scripts (copy from §9)
 
# 6. Verify
npm run lint
npm run format:check
git commit --allow-empty -m "test hook"   # should run lint-staged

That’s it. Same recipe, every repo.

🪴 Musings with Randheer

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setup-linting-formatting-precommit

Setting up ESLint + Prettier + Husky + lint-staged in a TypeScript repo

1. Why are we doing this?

2. Prerequisites

3. Install ESLint (modern flat config, ESLint v9+)

Install

Add npm scripts

Sanity check the generated config

Verify

4. Install Prettier and integrate with ESLint

Install

Configure Prettier — .prettierrc.json

Tell Prettier what to skip — .prettierignore

Wire Prettier into ESLint — update eslint.config.mts

Add format scripts

Verify

5. Install Husky (Git hooks)

Install

Verify it’s wired up

6. Install lint-staged and wire everything together

Install

Configure — add to package.json (top level, NOT under scripts)

Wire husky’s pre-commit hook to call lint-staged

Verify the full pipeline

7. What to do about the existing mess

Option A — clean baseline (recommended)

Option B — soft baseline

8. Will this break my build or deploy?

9. Final file checklist

12. Recap — replicating this in a new repo

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Configure Prettier — `.prettierrc.json`

Tell Prettier what to skip — `.prettierignore`

Wire Prettier into ESLint — update `eslint.config.mts`

Configure — add to `package.json` (top level, NOT under `scripts`)