Node.js and npm: project scripts and dependencies

Browser and Node.js environments

Both execute JavaScript but expose different APIs. document and the DOM belong to browsers; Node.js provides facilities such as filesystem APIs. A DOM example cannot run directly as a Node.js script without an additional DOM environment.

package.json and scripts

package.json describes package configuration. scripts assigns names to commands. In a practice folder, create this file and saludo.js containing console.log("Hello"). Run npm run saludo.

{
  "name": "library-example",
  "private": true,
  "scripts": {
    "saludo": "node saludo.js"
  }
}

Runtime and development dependencies

dependencies declares packages needed to use the distributed project. devDependencies commonly holds tests and build tools. A deployed application may need those tools during its build even if the final output does not use them at runtime.

install, lockfile and ci

npm install can update package-lock.json, which records the resolved dependency tree. npm ci requires a lockfile, fails on a package.json mismatch and removes node_modules before installation. It installs the whole project, not an individual new package.

node --version
npm --version
npm run saludo
# In a project with a compatible package-lock.json:
npm ci

Before running someone else’s project

Read scripts and Node.js requirements. Package installation and scripts can execute code; use known sources. Preserve the lockfile and review team and CI installation before changing package managers.

Practice

1. Run saludo and verify Hello is printed.
2. Rename the file without changing the script and observe the path error.
3. Fix the script and check the correction addresses that error.