[node.js] What is the --save option for npm install?

Update npm 5:

As of npm 5.0.0, installed modules are added as a dependency by default, so the --save option is no longer needed. The other save options still exist and are listed in the documentation for npm install.

Original answer:

Before version 5, NPM simply installed a package under node_modules by default. When you were trying to install dependencies for your app/module, you would need to first install them, and then add them (along with the appropriate version number) to the dependencies section of your package.json.

The --save option instructed NPM to include the package inside of the dependencies section of your package.json automatically, thus saving you an additional step.

In addition, there are the complementary options --save-dev and --save-optional which save the package under devDependencies and optionalDependencies, respectively. This is useful when installing development-only packages, like grunt or your testing library.

Examples related to node.js

Hide Signs that Meteor.js was Used Querying date field in MongoDB with Mongoose SyntaxError: Cannot use import statement outside a module Server Discovery And Monitoring engine is deprecated How to fix ReferenceError: primordials is not defined in node UnhandledPromiseRejectionWarning: This error originated either by throwing inside of an async function without a catch block dyld: Library not loaded: /usr/local/opt/icu4c/lib/libicui18n.62.dylib error running php after installing node with brew on Mac internal/modules/cjs/loader.js:582 throw err DeprecationWarning: Buffer() is deprecated due to security and usability issues when I move my script to another server Please run `npm cache clean`

Examples related to npm

What does 'x packages are looking for funding' mean when running `npm install`? error: This is probably not a problem with npm. There is likely additional logging output above Module not found: Error: Can't resolve 'core-js/es6' Browserslist: caniuse-lite is outdated. Please run next command `npm update caniuse-lite browserslist` ERROR in The Angular Compiler requires TypeScript >=3.1.1 and <3.2.0 but 3.2.1 was found instead DeprecationWarning: Buffer() is deprecated due to security and usability issues when I move my script to another server Please run `npm cache clean` What exactly is the 'react-scripts start' command? On npm install: Unhandled rejection Error: EACCES: permission denied Difference between npx and npm?