package.json

Scripts

Every script we define has pre and post version to it

• ex. if we define a install script, then there is a preinstall that is implicitly defined

Dependencies

• ^2.2.3 means >=2.2.3 AND <3.X

Peer Dependencies

peer dependencies are not automatically installed like dependencies and devDependencies are.

• Instead, when we list a package as a peerDependency, we expect it to be provided from the host (the host would be our application)

peer dependencies are most likely to be used only when creating npm packages.

• ex. react-dom lists react as a peerDependency, since react-dom is useless unless we have react installed.
  • if react-dom had listed react as a dependency, then effectively we would have 2 different versions of react in our project.
  • by listing react as a peerDependency, react-dom is basically saying "hey npm, I don't have react as a dependency, but I do need react to work. If someone tries to install me, but they don't have react installed, spit a warning at them, cause I ain't gonna work properly"

more info

Alias package names

We can alias our package names however we want to control how we import them in our code:

"pouchdb-core-react-native": "npm:@craftzdog/pouchdb-core-react-native@7.2.2",

Here, we are using the npm protocol to specify which package we'd like to install, and we set it to pouchdb-core-react-native.

• this can be helpful if we are trying to get DefinitelyTyped declaration files to work with a package where the name differs from the DefinitelyTyped version (which would occur, for example, if we were using a fork of the library, which we are in the above example)

Resolutions

resolutions is simply a map of package names and the exact versions of those packages that should be kept in the dependency tree

• ex. this configuration will remove all versions of webpack that are not 5.6.0. As long you install webpack@5.6.0 version as a dependency of the project you are working with, this will guarantee that all packages load the same version of webpack.

{
	"resolutions": {
		"webpack": "5.6.0"
	}
}

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The scripts section of package.json has access to the commands provided by node_modules. for instance, we can make a script that calls jest. We can't do this in our shell because it doesn't have access to the package by default. we'd have to manually go into node_modules to do that. But the commands are loaded into the shell that is openeed when we run scripts in package.json

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Backlinks

• Javascript Imports