[Bash] Use jq and grep to Find Unused Dependencies in a Project

In this lesson, we'll apply our jq skills and write a script that gets a list of dependencies from package.json and greps for usages of every package. If a package is unused, it's marked for removal.

Get 'dependencies' from package.json

jq '.dependencies' package.json

## {"express": "^4.16.4", "lodash": "^4.17.11"}

Only get keys for dependencies:

jq '.dependencies | keys | .[]' package.json

## "express"
## "lodash"

Then drop the `"``

jq -r '.dependencies | keys | .[]' package.json

## express
## lodash

Creat check-unused-deps.sh:

for dep in $(jq -r '.dependencies | keys | .[]' package.json); do
    if ! grep "require\(.*$dep.*\)" -Rq --exclude-dir="node_modules" .; then
        echo "You can probably remove $dep"
    fi
done

Give premission:

chmod +x check-unused-deps.sh

After running, it shows which deps can be removed for node applications.