How to check if npm script exists? - bash

Question

I am creating a bash script which runs through each of my projects and runs npm run test if the test script exists.
I know that if I get into a project and run npm run it will give me the list of available scripts as follows:
Lifecycle scripts included in www:
start
node server.js
test
mocha --require #babel/register --require dotenv/config --watch-extensions js **/*.test.js
available via `npm run-script`:
dev
node -r dotenv/config server.js
dev:watch
nodemon -r dotenv/config server.js
build
next build
However, I have no idea how to grab that information, see if test is available and then run it.
Here is my current code:
#!/bin/bash
ROOT_PATH="$(cd "$(dirname "$0")" && pwd)"
BASE_PATH="${ROOT_PATH}/../.."
while read MYAPP; do # reads from a list of projects
PROJECT="${MYAPP}"
FOLDER="${BASE_PATH}/${PROJECT}"
cd "$FOLDER"
if [ check here if the command exists ]; then
npm run test
echo ""
fi
done < "${ROOT_PATH}/../assets/apps-manifest"

Answer 1

EDIT:
As mentioned by Marie and James if you only want to run the command if it exists, npm has an option for that:
npm run test --if-present
This way you can have a generic script that work with multiple projects (that may or may not have an specific task) without having the risk of receiving an error.
Source: https://docs.npmjs.com/cli/run-script
EDIT
You could do a grep to check for the word test:
npm run | grep -q test
this return true if the result in npm run contains the word test
In your script it would look like this:
#!/bin/bash
ROOT_PATH="$(cd "$(dirname "$0")" && pwd)"
BASE_PATH="${ROOT_PATH}/../.."
while read MYAPP; do # reads from a list of projects
PROJECT="${MYAPP}"
FOLDER="${BASE_PATH}/${PROJECT}"
cd "$FOLDER"
if npm run | grep -q test; then
npm run test
echo ""
fi
done < "${ROOT_PATH}/../assets/apps-manifest"
It just would be a problem if the word test is in there with another meaning
Hope it helps

Answer 2

The right solution is using the if-present flag:
npm run test --if-present

Answer 3

--if-present doesn't allow you to "check if a npm script exists", but runs the script if it exists. If you have fallback logic this won't suffice. In my case, I want to run npm run test:ci if it exists and if not check for and run, npm run test. Using --if-present would run the test:ci AND test scripts if both exists. By checking if one exists first, we can decide which to run.
Because I have both "test" and "test:ci" scripts, the npm run | grep approach wasn't sufficient. As much as I'd like to do this with strictly npm, I have jq in my environments so I decided to go that route to have precision.
To check for a script named "test:ci":
if [[ $(jq '.scripts["test:ci"]' < package.json;) != null ]]; then
// script exists
fi