Pre-commit hook for eslint, linting *only* staged changes.

pre-commit.sh

#!/bin/bash

for file in $(git diff --cached --name-only | grep -E '\.(js|jsx)$')
do
  git show ":$file" | node_modules/.bin/eslint --stdin --stdin-filename "$file" # we only want to lint the staged changes, not any un-staged changes
  if [ $? -ne 0 ]; then
    echo "ESLint failed on staged file '$file'. Please check your code and try again. You can run ESLint manually via npm run eslint."
    exit 1 # exit with failure status
  fi
done

This does not lint "only staged changes" it lints each file that is changed. Which is annoying because it can block your commit for stuff that isn't even in the commit! Eslint should just have a --diff options like flake8

There is an cleaner way to accomplish this, with husky:

// package.json
...
"husky": {
    "hooks": {
      "pre-commit": "lint-staged"
    }
  },
  "lint-staged": {
    "*.{js,ts,tsx}": [
      "prettier --write",
      "eslint --ext .ts,.tsx,.js --fix"
    ]
  },

@aperkaz

https://www.npmjs.com/package/eslint-plugin-diff

@aperkaz

LGTM, but maybe eslint should be run before prettier.

Note: If you use ESLint, make sure lint-staged runs it before Prettier, not after.
ref: https://prettier.io/docs/en/install.html#git-hooks

There is an cleaner way to accomplish this, with husky:

// package.json
...
"husky": {
    "hooks": {
      "pre-commit": "lint-staged"
    }
  },
  "lint-staged": {
    "*.{js,ts,tsx}": [
      "prettier --write",
      "eslint --ext .ts,.tsx,.js --fix"
    ]
  },

this worked for me & I also took @zhyd1997's suggestion

  },

@aperkaz
Where exactly i need to place above lines inside package.json file.

@Naveen9453 after the dependencies section is a good place, although I tend to locate it at the end of the file. No strict placement requirements though.

package.json configuration of husky no longer works, by design.