run eslint only on changed (*.js files) files using pre-commit

package.json

{
  "scripts": {
    "eslint": "LIST=`git diff-index --name-only HEAD~1 | grep .*\\.js | grep -v json`; if [ \"$LIST\" ]; then eslint $LIST; fi"
  },
  "devDependencies": {
    "eslint": "~0.5.1"
  },
  "pre-commit": [
    "eslint"
  ]
}