anything starting with npm_config_ is general npm configuration from your global npm config or from a project specific.When you run a command or script through npm run., your environment variables will automatically be augmented with a set of variables from npm.Īll environment variables are prefixed with npm_ and can be grouped into two types: The next thing was a pleasant surprise for me the first time I discovered it.

You can read more about those lifecycle scripts in the npm docs. Where the difference between version and postversion is that postversion will be called after npm has committed the changes performed in preversion and version. An odd one here is version because it provides preversion, version and postversion. The same behavior also applies for built-in commands.

downloading data before building your application.

It's a great way to chain commands without convoluting your scripts. This works because npm will automatically detect if a script has other scripts named the same way but prefixed with pre or post and will execute those in the respective order.

test is executed running the jest test runner.

postbuild will be called running npm run test.

build is executed running the TypeScript compiler.

prebuild will be called executing the rimraf tool to delete the dist folder.

If you now run npm run build the following things will automatically be triggered: įor example if our package.json looks like this: These can then be executed using npm run. The scripts field holds an object where you can specify various commands and scripts you want to expose. When we talk about 'npm scripts' we are talking about entries in the scripts field of the package.json. Everything in this post has been tested with npm version 6.10. While a lot of these things should work in yarn, berry and pnpm as well, we'll focus on npm in this article. In this blog post we'll talk about the most useful and some hidden features.īefore we get started, make sure you have the latest version of npm installed. While you might have used this to set up your 'build', 'dev' or 'start' script, there's a lot of things you can do with them. This is where 'npm scripts' come into place. However, sometimes you still have the need for very custom configurations and scripts. The Node.js ecosystem is full with useful CLI tools and most of them offer configurations that let you tune them to do exactly what you want.

Npm config set for project