ESLint executing on changed files as a git precommit hook

pre-commit

#!/bin/bash -u

# 
# Run eslint on js and jsx files that are being committed, including doing a round of fixing up
# those files.
#
# Based on @dahjelle/pre-commit.sh and @jancimajek's one liner in that Gist.
#

NAMES=`git diff --diff-filter=d --cached --name-only -- '*.js' '*.jsx' | wc -l`
if [ ${NAMES} -eq 0 ]; then

  echo "No files to check with eslint" 

else

  # Ensures that eslint exists and die if it is not
  which eslint || ( echo "Please install eslint"; exit -1 )

  # ESLint staged changes within patient-mobile/bsncAppExpo only
  git diff --diff-filter=d --cached --name-only -z -- '*.js' '*.jsx' \
    | xargs -0 -I % sh -c 'eslint --cache --report-unused-disable-directives --quiet --color --fix "%" 1>/dev/null; git add "%";'
  git diff --diff-filter=d --cached --name-only -z -- '*.js' '*.jsx' \
    | xargs -0 -I % sh -c 'git show ":%" | eslint --cache --color --quiet --stdin --stdin-filename "%";'
  eslint_exit=$?

  if [ ${eslint_exit} -eq 0 ]; then
    git diff --diff-filter=d --cached --name-only -z -- '*.js' '*.jsx' \
      | xargs -0 -I % sh -c 'git show ":%" | eslint --max-warnings=0 --cache --color --stdin --stdin-filename "%";'
    eslint_exit=$?
    if [ ${eslint_exit} -eq 0 ]; then
      echo "✓ ESLint passed"
    else
      echo "✘ ESLint failed with warnings!" 1>&2
      echo "But we're letting it run anyway...just warnings."
    fi
  else
    echo "✘ ESLint failed with errors!" 1>&2
    exit ${eslint_exit}
  fi

fi


#
# Run jq on json files that are being committed.
#

NAMES=`git diff --diff-filter=d --cached --name-only -- '*.json' '*.json5' | wc -l`
if [ ${NAMES} -eq 0 ]; then

  echo "No files to check with jq" 

else

  # Ensures that eslint exists and die if it is not
  which jq || ( echo "Please install 'jq' for analyzing/verifying JSON files"; exit -1 )

  # ESLint staged changes within patient-mobile/bsncAppExpo only
  git diff --diff-filter=d --cached --name-only -z -- '*.json' '*.json5' \
    | xargs -0 -I % sh -c 'git show ":%" | jq . 1>/dev/null'
  jq_exit=$?

  if [ ${jq_exit} -eq 0 ]; then
    echo "✓ JSON syntax check passed"
  else
    echo "✘ JSON syntax check failed with errors!" 1>&2
    exit ${jq_exit}
  fi

fi