When to use --save and --save-dev in NPM?

Question

Node.js

When to use --save and --save-dev in NPM?

Answer 1

Compilers-transpilers-translators (like Coffee, LESS, Jade), test runners, style checkers and linters (mocha, chai, karma, (js|es)lint, jscs), plugins for task runners (grunt-contrib- watch, gulp-jade) - all this is usually set as --save-dev, because only those who contribute to this project need to work with its code.
Libraries and frameworks (expressjs, jquery, backbone), on the basis of which your code works, without which your code will not run on its consumer, are set as --save.

Answer 2

If you want npm to modify the dependencies in package.json, and dependencies are known to be divided into main (dependencies) and development (devDependencies). Development dependencies are installed via npm install packageName --dev and this is used for automated testing, builds, etc.