Bash script to grep for unused dependencies in a node.js project

grep-for-dependencies.sh

set -e

# function to grep for a dependency
grep_dep() {
  # params: $1 = the string to grep for, $2 = directory to grep in
  
  # [1]
  grep --include="*.js" --exclude-dir="node_modules" -R --color -n "require\(.*$1.*\)" "$2"

  # if grep returns 0 results, it has an exit code of 1. No results means dependency is not in use
  if [[ $? > 0 ]]; then
    echo
    echo "** No uses of $1 found, consider removing. **"
    echo
  fi
}

# [2]
export -f grep_dep

# [3]
jq -r '.dependencies | keys | .[]' package.json | \
  # [4]
  xargs -I '{}' -P 4 -t bash -c "grep_dep '{}' ."