Difference between dependencies and dev-dependencies?

In your node project in the file package.json, you may have seen two similar JSON element:

“dependencies”: {

            …

}

 and

“devDependencies” : {

            …

}

devDependencies contains modules which are only required during development.

To save a module as devDependencies on installation, we do:

npm install <module-name> --save-dev

or shortcut:

npm i <module-name> -D

Some examples of dev dependencies are Jest, Chai, Nodemon, Babel, etc.

dependencies contains modules that are required at runtime.

To save a module as run time dependencies, we do:

npm install <module-name> --save

or shortcut:

npm i <module-name> -S

Some examples of runtime dependencies are Express, React, Apollo-client etc.