package.jsonThe best way to manage locally installed npm packages is to create a
package.json file.
A package.json file affords you a lot of great things:
As a bare minimum, a package.json must have:
"name"
"version"For example:
{ "name": "my-awesome-package", "version": "1.0.0"}
package.jsonTo create a package.json run:
> npm init
This will initate a command line questionaire that will conclude with the
creation of a package.json in the directory you initiated the command.
--yes init flagThe extended CLI Q&A experience is not for everyone, and often if you are
comfortable with using a package.json you'd like a more expedited
experience.
You can get a default package.json by running npm init with the --yes
or -y flag:
> npm init --yes
This will ask you only one question, author. Otherwise it will fill in default
values:
> npm init --yesWrote to /home/ag_dubs/my_package/package.json: { "name": "my_package", "version": "1.0.0", "main": "index.js", "scripts": { "test": "echo \"Error: no test specified\" && exit 1" }, "keywords": [], "author": "ag_dubs", "license": "ISC", "repository": { "type": "git", "url": "https://github.com/ashleygwilliams/my_package.git" }, "bugs": { "url": "https://github.com/ashleygwilliams/my_package/issues" }, "homepage": "https://github.com/ashleygwilliams/my_package"}
name: defaults to author name unless in a git directory, in which case it
will be the name of the repositoryversion: always 1.0.0main: always index.jsscripts: by default creates a empty test scriptkeywords: emptyauthor: whatever you provided the CLIlicense: ISCrepository: will pull in info from the current directory, if presentbugs: will pull in info from the current directory, if presenthomepage: will pull in info from the current directory, if presentYou can also set several config options for the init command. Some useful ones:
> npm set init.author.email "wombat@npmjs.com"> npm set init.author.name "ag_dubs"> npm set init.license "MIT"
If there is no description field in the package.json, npm uses the first line of the README.md or README instead. The description helps people find your package on npm search, so it's definitely useful to make a custom description in the package.json to make your package more discoverable.
To specify the packages your project depends on, you need to
list the packages you'd like to use in your package.json file. There are
2 types of packages you can list:
"dependencies": these packages are required by your application in production"devDependencies": these packages are only needed for development and testingpackage.jsonYou can manually edit your package.json. You'll need to create an attribute
in the package object called dependencies that points to an object. This object
will hold attributes named after the packages you'd like to use, that point to a
semver expression that specifies what versions of that project are
compatible with your project.
If you have dependencies you only need to use during local development, you will
follow the same instructions as above but in an attribute called devDependencies.
For example: The project below uses any version of the package my_dep that matches
major version 1 in production, and requires any version of the package my_test_framework
that matches major version 3, but only for development:
{ "name": "my_package", "version": "1.0.0", "dependencies": { "my_dep": "^1.0.0" }, "devDependencies" : { "my_test_framework": "^3.1.0" }}
--save and --save-dev install flagsThe easier (and more awesome) way to add dependencies to your package.json is to do
so from the command line, flagging the npm install command with either --save or
--save-dev, depending on how you'd like to use that dependency.
To add an entry to your package.json's dependencies:
npm install <package_name> --save
To add an entry to your package.json's devDependencies:
npm install <package_name> --save-dev
npm uses Semantic Versioning, or, as we often refer to it, SemVer, to manage versions and ranges of versions of packages.
If you have a package.json file in your directory and you run
npm install, then npm will look at the dependencies that are listed in
that file and download the latest versions satisfying semver rules
for all of those.
To learn more about semantic versioning, check out our Getting Started "Semver" page.
Last modified February 11, 2016 Found a typo? Send a pull request!