Installing packages (dependencies vs devDependencies) in Node.js - Practice Exercises

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding dependencies vs devDependencies

Which statement correctly describes the difference between dependencies and devDependencies in a Node.js project?

A dependencies are required for the app to run in production, devDependencies are only needed during development

B devDependencies are installed globally, dependencies are installed locally

C dependencies and devDependencies are the same and can be used interchangeably

D dependencies are needed only during development, devDependencies are needed in production

💡 Hint

Think about which packages your app needs when it runs versus when you write or test it.

Dependencies are packages your app needs to run in production. DevDependencies are only needed during development, like testing or building tools.

❓ component_behavior

intermediate

Effect of installing a package with --save-dev

What happens when you run npm install eslint --save-dev in your project?

A eslint is installed globally and not added to package.json

B eslint is added to dependencies and installed

C eslint is added to devDependencies and installed

D eslint is added to dependencies but not installed

💡 Hint

Consider where the package is listed in package.json after this command.

The --save-dev flag adds the package to devDependencies and installs it locally.

📝 Syntax

advanced

Identifying correct package.json entry for dependencies

Given this snippet from package.json, which option correctly shows how a dependency should appear?

Node.js

{
  "dependencies": {
    "express": "^4.18.2"
  },
  "devDependencies": {
    "jest": "^29.5.0"
  }
}

A "express": "^4.18.2"

B "express": "4.18.2"

C "express": "~4.18.2"

D "express": "*"

💡 Hint

Look for the caret symbol and what it means for versioning.

The caret (^) means compatible with version 4.18.2, allowing minor updates but not major ones.

❓ state_output

advanced

Result of running npm install without package-lock.json

If your project has a package.json with dependencies and devDependencies but no package-lock.json, what will happen when you run npm install?

A No packages are installed because package-lock.json is missing

B Only dependencies are installed, devDependencies are ignored

C Only devDependencies are installed, dependencies are ignored

D Both dependencies and devDependencies are installed locally

💡 Hint

Think about what npm does by default when installing packages.

By default, npm install installs both dependencies and devDependencies locally, even if package-lock.json is missing.

🔧 Debug

expert

Why does a package installed as devDependency fail in production?

You installed a package with npm install --save-dev some-package. Your app crashes in production saying the package is missing. Why?

A The package was installed globally and not included in the project

B devDependencies are not installed when running <code>npm install --production</code> in production

C The package version is incompatible with production Node.js version

D The package.json file is corrupted and missing the package entry

💡 Hint

Consider what happens when you install packages in production mode.

When running npm install --production, npm skips installing devDependencies, so the package is missing in production.