What is npm?
npm is a package manager for NodeJS. It is also the largest single language code repository on earth and a tool for installing and managing packages from the repository on the command line.
What is a package?
The npm registry consists of numerous packages or libraries that can be downloaded, installed, and used as a dependency in a NodeJS project. An npm package is a reusable piece of code published to the npm registry. It helps developers improve their workflow by incorporating functionality, thereby reducing the need to write redundant or repetitive code.
How do I install a package in my NodeJS project?
By using the CLI command npm install
- npm install: This command will install all the dependencies mentioned in the package.json in the node_modules folder.
-
npm install
: Installs the package in the current project directory (inside the node_modules folder). The package is accessible only within that project. -
npm install -g
: Installs the package system-wide, making it available from anywhere on your machine. -
npm install
@ : Installs a specific version of that package. -
npm install
--save-dev: Installs the package and puts it in the devDependencies block of package.json -
npm install
--no-save: Installs the package but does not add the entry to the package.json file dependencies. -
npm install
--save-optional: Installs the package and adds the entry to the package.json file's optionalDependencies -
npm install
--no-optional: This will prevent the installation of optional dependencies.
What is package.json?
package.json is a configuration file used in Node.js projects to manage project metadata, dependencies, and scripts. It acts as the heart of a NodeJS project.
What is the difference between devDependencies and peerDependencies?
devDependencies: These are packages and libraries needed only during development or testing. They are not included in the production code.
Installation:
npm install tslint --save-dev
peerDependencies: These are dependencies that the project needs to work on, but it expects the user who is installing the package to provide the dependency.
"peerDependencies": { "graphql": ">=10.0.0" }
The above block means:
- The project needs the package graphql to work.
- It needs the version of the graphql package to be 10.0.0 or higher.
- The package users must install GraphQL themselves.
Scripts in package.json
The scripts field in package.json defines commands that can be run using npm run

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