Why is npm running prepare script after npm install, and how can I stop it?

Question

Whenever I run npm install <package> it installs the package alright, but then it automatically runs the prepare script.

It's worth mentioning that I've already checked that there is no postinstall script in the package.json.

Answer 1

From https://docs.npmjs.com/misc/scripts:

prepare: Run both BEFORE the package is packed and published, and on local npm install without any arguments (See below). This is run AFTER prepublish, but BEFORE prepublishOnly.

Since NPM v5, prepare script is executed when you run npm install

Answer 2

The other answers are fine, but for some additional context, this is to support a workflow where you can use devDependencies to build assets or other generated content for your project.

For example, say you want to use node-sass (CSS preprocessor). You add "node-sass" as a devDependency, then you run the sass command in your "prepare" script, which generates your CSS.

So, when you run npm install, the following happens:

• dependencies and devDependencies get installed
• your "prepare" script generates your CSS
• your project is ready to go with all necessary CSS

And when you run npm publish, something similar happens:

• your "prepare" script generates your CSS
• your code and generated CSS are published to the npm repo

So now when someone comes along and installs your package, they don't need node-sass or any of your devDependencies. They only need to runtime deps.