Yash Kalaria for BoTreeTechnologies

Posted on Dec 9, 2019 • Updated on Aug 21, 2021

[2021] Setting up Husky pre-commit hook with ESLint, Prettier and lint-staged for React and React Native.

#react #reactnative #javascript #beginners

Hello folks. I hope you all are doing well.
In this post, we will talk about how you can setup Husky pre-commit hook with ESLint, Prettier and lint-staged to avoid bad commits and properly format code before committing. So let's get into it.

What is Husky?

Husky lets us run commands or script before committing or pushing our code to git. There are a lot of other use cases of Husky too but we will only be using pre-commit hook for this article.

What is ESLint?

ESLint is a tool that can analyze our code and find errors in that code using ESLint rules. It can also fix some errors on its own.

What is Prettier?

Prettier is an opinionated code formatter that can format our code with the help of rules that you set or defaults are used.

What is lint-staged?

lint-staged can run multiple linters against staged git files which in our case are ESLint and Pretttier.

Setup new React or React Native project.

For React use
npx create-react-app demo
cd demo

For React Native use
npx react-native init demo
cd demo

Let's install some necessary libraries.

npm i -D husky lint-staged eslint-config-airbnb prettier

Here we are saving these modules as devDependencies to specify that these are only required in the development and not in runtime. I am using Airbnb's pre config file for ESLint. You can also go plain if you want to setup all ESLint rules by your self or you can also extend multiple pre configs like this.

Setting up ESLint

Replace or create .eslintrc.js file with the following code. If you have created a React project then remove "eslintConfig" from the package.json file as we have created a separate configuration file for the ESLint.

It is advisable to extend "react-app" for React projects and "@react-native-community" for React Native projects. These files are automatically installed so you don't need to worry about them. Just append this to the start of the array in the extend option in the file.

Setting up Prettier

Replace or create .prettierrc.js file with the following code.

Setting up Husky pre-commit hook and lint-staged

In the latest versions of Husky we need to enable Git Hooks and then create and add the pre-commit hook. To do that run the following commands in the terminal.
npx husky install
npx husky add .husky/pre-commit "npx --no-install lint-staged"

Make sure to commit the auto-generated husky folder to your Git repo.

The above code will run lint-staged command against the staged files before committing. Make sure to run npx husky install if you clone your Husky configured git repo.

So now let's add the lint-staged in our package.json file.

Open your package.json file and add the code that I have specified at the same level as dependencies.

The above code will run Prettier and ESLint rules against all js,jsx,ts,tsx staged files. You can also specify more file extensions or you can write a script for a specific folder you want.

Read Also: How React Native Improves Developer Productivity

So yeah that's it. Now when you will try to commit any changes, ESLint and Prettier rules will execute and it will format your code and give you errors if there are any and stop you from causing any bad commits.

Note: If you get dependency errors for eslint-plugin-jsx-a11y or eslint-plugin-import while commiting, then also install them as devDependencies.

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Top comments (13)

Comment hidden by post author - thread only accessible via permalink

Kenny To • Aug 9 '20

I had dependencies issues with eslint as a devDependency, since React requires version 6.8.0. Not sure why it didn't resolve itself. Just incase anybody runs into this in the future., you can skip installing eslint and let the project manage the dependencies by itself.

Yash Kalaria • Aug 21 '21

Updated for 2021 with all the fixes.

Comment hidden by post author - thread only accessible via permalink

Prateek Maheshwari • Jun 15 '20

Just a query, you said the above code will run Prettier and ESLint rules against all js,jsx,ts,tsx files in the src directory OR will it run for all the specified files in src which are STAGED?

Yash Kalaria • Jun 17 '20

It will run for all the js,jsx,ts,tsx files in the src directory whether they are staged or not.

Prateek Maheshwari • Jun 17 '20

How can we make it run for only staged files. I am stuck with this in my project because the eslint takes too much time as it runs on all files in the directory.

Yash Kalaria • Jun 17 '20 • Edited

Try replacing your "lint" command in package.json with below command and if that works then you can do something similar for prettier too.

"lint": "eslint src/**/**/*.js --fix-dry-run git diff --diff-filter=d --cached --name-only | grep -E './**/*.(js|jsx|ts|tsx|css|scss|md)$'"

Nithin • Jun 23 '20 • Edited

Thanks for the post Yash, it was very helpful. Just wanted to point out that I don't think this is necessary. Correct me if I'm wrong, but from the lint-staged documentation and from what I see from my own project after setting this up, linting runs for only the files which are staged and also match the specified glob pattern.

"husky": {
"hooks": {
"pre-commit": "lint-staged"
}
},
"lint-staged": {
"*.{js,jsx,ts,tsx}": [
"npx prettier --write",
"eslint --ext .js,.jsx --fix-dry-run"
]
}

I used this setting and it only throws lint errors for staged changes while I commit even though there are other unstaged files with lint errors.

I think the line to note is
"eslint src/*.js --fix-dry-run" which you've mentioned.

I've used "eslint --ext .js,.jsx --fix-dry-run" without specifying a target, so that it doesn't run for all files in the src directory, only the staged files that are fed into this command by lint-staged.