Installing and running a project

You have a project folder. Now what?

package.json — the project's description

Almost every JavaScript project has a file called package.json at its root. Read it first:

cat package.json

{"name": "site", "scripts": {"start": "node app.js", "build": "node build.js"}}

Two things matter to you right now:

• dependencies — the libraries this project needs to work
• scripts — named shortcuts for commands the project runs often

npm install — get what it needs

npm install

npm reads the dependency list and downloads every package into a folder called node_modules.

That folder gets big — thousands of files — which is exactly why it is never committed to a repository. The list of dependencies is shared; the downloaded copies are rebuilt on each machine by running npm install.

npm run — do what it offers

Scripts are commands the project’s authors named for convenience. See what exists:

npm run

Lifecycle scripts:
  start
    node app.js
  build
    node build.js

Then run one by name:

npm run start

The key thing to understand: npm run build does not have a fixed meaning. It runs whatever this project defined under build. In one project that compiles a website; in another it packages a library. cat package.json is how you find out which.

The shape of every project setup

It is always these three steps, in this order:

1. cat package.json — see what you are dealing with.
2. npm install — get the dependencies.
3. npm run <something> — start it.

When an AI agent sets up a project for you, this is what it is doing. Recognising the pattern is what lets you tell “normal setup” from “wait, why is it doing that”.

Try it

1. cat package.json — read the scripts.
2. npm install — fetch the dependencies.
3. npm run — list what the project offers.
4. npm run start — run one.

Step 3 is the habit worth keeping. Ask the project what it can do before guessing at command names.