Ubuntu Manpage: package.json - Specifics of npm's package.json handling

NAME

       package.json - Specifics of npm's package.json handling

DESCRIPTION

       This document is all you need to know about what's required in your package.json file.  It
       must be actual JSON, not just a JavaScript object literal.

       A lot of the behavior described in this  document  is  affected  by  the  config  settings
       described in npm help 7 npm-config.

name

If you plan to publish your package, the most important things in your package.json are
the name and version fields as they will be required. The name and version together form
an identifier that is assumed to be completely unique. Changes to the package should come
along with changes to the version. If you don't plan to publish your package, the name and
version fields are optional.

The name is what your thing is called.

Some rules:

· The name must be less than or equal to 214 characters. This includes the scope for
scoped packages.

· The name can't start with a dot or an underscore.

· New packages must not have uppercase letters in the name.

· The name ends up being part of a URL, an argument on the command line, and a folder
name. Therefore, the name can't contain any non-URL-safe characters.

Some tips:

· Don't use the same name as a core Node module.

· Don't put "js" or "node" in the name. It's assumed that it's js, since you're writing a
package.json file, and you can specify the engine using the "engines" field. (See
below.)

· The name will probably be passed as an argument to require(), so it should be something
short, but also reasonably descriptive.

· You may want to check the npm registry to see if there's something by that name already,
before you get too attached to it. https://www.npmjs.com/

A name can be optionally prefixed by a scope, e.g. @myorg/mypackage. See npm help 7
npm-scope for more detail.

version

       If you plan to publish your package, the most important things in  your  package.json  are
       the  name  and version fields as they will be required. The name and version together form
       an identifier that is assumed to be completely unique.  Changes to the package should come
       along with changes to the version. If you don't plan to publish your package, the name and
       version fields are optional.

       Version must be parseable by node-semver https://github.com/isaacs/node-semver,  which  is
       bundled with npm as a dependency.  (npm install semver to use it yourself.)

       More on version numbers and ranges at npm help 7 semver.

description

       Put a description in it.  It's a string.  This helps people discover your package, as it's
       listed in npm search.

keywords

       Put keywords in it.  It's an array of strings.  This helps people discover your package as
       it's listed in npm search.

homepage

       The url to the project homepage.

       Example:

         "homepage": "https://github.com/owner/project#readme"

bugs

       The  url to your project's issue tracker and / or the email address to which issues should
       be reported. These are helpful for people who encounter issues with your package.

       It should look like this:

         { "url" : "https://github.com/owner/project/issues"
         , "email" : "project@hostname.com"
         }

       You can specify either one or both values. If you want to provide  only  a  url,  you  can
       specify the value for "bugs" as a simple string instead of an object.

       If a url is provided, it will be used by the npm bugs command.

license

       You  should  specify a license for your package so that people know how they are permitted
       to use it, and any restrictions you're placing on it.

       If you're using a common license such as BSD-2-Clause or MIT, add a current  SPDX  license
       identifier for the license you're using, like this:

         { "license" : "BSD-3-Clause" }

       You  can  check the full list of SPDX license IDs https://spdx.org/licenses/.  Ideally you
       should pick one that is OSI https://opensource.org/licenses/alphabetical approved.

       If your package is licensed under multiple common licenses, use an SPDX license expression
       syntax version 2.0 string https://npmjs.com/package/spdx, like this:

         { "license" : "(ISC OR GPL-3.0)" }

       If  you  are  using  a license that hasn't been assigned an SPDX identifier, or if you are
       using a custom license, use a string value like this one:

         { "license" : "SEE LICENSE IN <filename>" }

       Then include a file named <filename> at the top level of the package.

       Some old packages used license objects or a "licenses" property  containing  an  array  of
       license objects:

         // Not valid metadata
         { "license" :
           { "type" : "ISC"
           , "url" : "https://opensource.org/licenses/ISC"
           }
         }

         // Not valid metadata
         { "licenses" :
           [
             { "type": "MIT"
             , "url": "https://www.opensource.org/licenses/mit-license.php"
             }
           , { "type": "Apache-2.0"
             , "url": "https://opensource.org/licenses/apache2.0.php"
             }
           ]
         }

       Those styles are now deprecated. Instead, use SPDX expressions, like this:

         { "license": "ISC" }

         { "license": "(MIT OR Apache-2.0)" }

       Finally,  if  you  do  not  wish to grant others the right to use a private or unpublished
       package under any terms:

         { "license": "UNLICENSED" }

       Consider also setting "private": true to prevent accidental publication.

people fields: author, contributors

       The "author" is one person.  "contributors" is an array  of  people.   A  "person"  is  an
       object with a "name" field and optionally "url" and "email", like this:

         { "name" : "Barney Rubble"
         , "email" : "b@rubble.com"
         , "url" : "http://barnyrubble.tumblr.com/"
         }

       Or you can shorten that all into a single string, and npm will parse it for you:

         "Barney Rubble <b@rubble.com> (http://barnyrubble.tumblr.com/)"

       Both email and url are optional either way.

       npm also sets a top-level "maintainers" field with your npm user info.

files

       The  optional  files  field  is an array of file patterns that describes the entries to be
       included when your package is installed as a dependency. File patterns  follow  a  similar
       syntax to .gitignore, but reversed: including a file, directory, or glob pattern (*, **/*,
       and such) will make it so that file is included in the tarball when it's packed.  Omitting
       the field will make it default to ["*"], which means it will include all files.

       Some  special  files  and  directories are also included or excluded regardless of whether
       they exist in the files array (see below).

       You can also provide a .npmignore file in the root of your package or  in  subdirectories,
       which  will  keep  files  from  being  included.  At  the root of your package it will not
       override the "files" field, but in subdirectories it will. The .npmignore file works  just
       like  a .gitignore. If there is a .gitignore file, and .npmignore is missing, .gitignore's
       contents will be used instead.

       Files included with the "package.json#files" field cannot be excluded  through  .npmignore
       or .gitignore.

       Certain files are always included, regardless of settings:

       · package.json

       · README

       · CHANGES / CHANGELOG / HISTORY

       · LICENSE / LICENCE

       · NOTICE

       · The file in the "main" field

       README, CHANGES, LICENSE & NOTICE can have any case and extension.

       Conversely, some files are always ignored:

       · .git

       · CVS

       · .svn

       · .hg

       · .lock-wscript

       · .wafpickle-N

       · .*.swp

       · .DS_Store

       · ._*

       · npm-debug.log

       · .npmrc

       · node_modules

       · config.gypi

       · *.orig

       · package-lock.json (use shrinkwrap instead)

main

       The  main  field is a module ID that is the primary entry point to your program.  That is,
       if your package is named foo, and a user installs it, and then does  require("foo"),  then
       your main module's exports object will be returned.

       This should be a module ID relative to the root of your package folder.

       For most modules, it makes the most sense to have a main script and often not much else.

browser

       If your module is meant to be used client-side the browser field should be used instead of
       the main field. This is helpful to hint users that it might rely on primitives that aren't
       available in Node.js modules. (e.g. window)

bin

       A  lot  of packages have one or more executable files that they'd like to install into the
       PATH. npm makes this pretty easy (in fact, it uses  this  feature  to  install  the  "npm"
       executable.)

       To  use  this,  supply  a bin field in your package.json which is a map of command name to
       local file name. On install, npm  will  symlink  that  file  into  prefix/bin  for  global
       installs, or ./node_modules/.bin/ for local installs.

       For example, myapp could have this:

         { "bin" : { "myapp" : "./cli.js" } }

       So,   when  you  install  myapp,  it'll  create  a  symlink  from  the  cli.js  script  to
       /usr/local/bin/myapp.

       If you have a single executable, and its name should be the name of the package, then  you
       can just supply it as a string.  For example:

         { "name": "my-program"
         , "version": "1.2.5"
         , "bin": "./path/to/program" }

       would be the same as this:

         { "name": "my-program"
         , "version": "1.2.5"
         , "bin" : { "my-program" : "./path/to/program" } }

       Please  make  sure  that  your  file(s) referenced in bin starts with #!/usr/bin/env node,
       otherwise the scripts are started without the node executable!

man

       Specify either a single file or an array of filenames to put in place for the man  program
       to find.

       If only a single file is provided, then it's installed such that it is the result from man
       <pkgname>, regardless of its actual filename.  For example:

         { "name" : "foo"
         , "version" : "1.2.3"
         , "description" : "A packaged foo fooer for fooing foos"
         , "main" : "foo.js"
         , "man" : "./man/doc.1"
         }

       would link the ./man/doc.1 file in such that it is the target for man foo

       If the filename doesn't start with the package name, then it's prefixed.  So, this:

         { "name" : "foo"
         , "version" : "1.2.3"
         , "description" : "A packaged foo fooer for fooing foos"
         , "main" : "foo.js"
         , "man" : [ "./man/foo.1", "./man/bar.1" ]
         }

       will create files to do man foo and man foo-bar.

       Man files must end with a number, and optionally a .gz suffix if they are compressed.  The
       number dictates which man section the file is installed into.

         { "name" : "foo"
         , "version" : "1.2.3"
         , "description" : "A packaged foo fooer for fooing foos"
         , "main" : "foo.js"
         , "man" : [ "./man/foo.1", "./man/foo.2" ]
         }

       will create entries for man foo and man 2 foo

directories

       The  CommonJS  Packages http://wiki.commonjs.org/wiki/Packages/1.0 spec details a few ways
       that you can indicate the structure of your package using a  directories  object.  If  you
       look  at  npm's package.json https://registry.npmjs.org/npm/latest, you'll see that it has
       directories for doc, lib, and man.

       In the future, this information may be used in other creative ways.

   directories.lib
       Tell people where the bulk of your library is.  Nothing  special  is  done  with  the  lib
       folder in any way, but it's useful meta info.

   directories.bin
       If  you  specify  a bin directory in directories.bin, all the files in that folder will be
       added.

       Because of the way the bin directive  works,  specifying  both  a  bin  path  and  setting
       directories.bin is an error. If you want to specify individual files, use bin, and for all
       the files in an existing bin directory, use directories.bin.

   directories.man
       A folder that is full of man pages.  Sugar to  generate  a  "man"  array  by  walking  the
       folder.

   directories.doc
       Put markdown files in here.  Eventually, these will be displayed nicely, maybe, someday.

   directories.example
       Put example scripts in here.  Someday, it might be exposed in some clever way.

   directories.test
       Put your tests in here. It is currently not exposed, but it might be in the future.

repository

       Specify  the  place  where  your  code  lives.  This  is  helpful  for  people who want to
       contribute.  If the git repo is on GitHub, then the npm docs command will be able to  find
       you.

       Do it like this:

         "repository" :
           { "type" : "git"
           , "url" : "https://github.com/npm/npm.git"
           }

         "repository" :
           { "type" : "svn"
           , "url" : "https://v8.googlecode.com/svn/trunk/"
           }

       The URL should be a publicly available (perhaps read-only) url that can be handed directly
       to a VCS program without any modification.  It should not be a url to an html project page
       that you put in your browser.  It's for computers.

       For  GitHub,  GitHub gist, Bitbucket, or GitLab repositories you can use the same shortcut
       syntax you use for npm install:

         "repository": "npm/npm"

         "repository": "github:user/repo"

         "repository": "gist:11081aaa281"

         "repository": "bitbucket:user/repo"

         "repository": "gitlab:user/repo"

scripts

       The "scripts" property is a dictionary containing script commands that are run at  various
       times  in the lifecycle of your package.  The key is the lifecycle event, and the value is
       the command to run at that point.

       See npm help 7 npm-scripts to find out more about writing package scripts.

config

       A "config" object can be used to set configuration parameters used in package scripts that
       persist across upgrades.  For instance, if a package had the following:

         { "name" : "foo"
         , "config" : { "port" : "8080" } }

       and   then  had  a  "start"  command  that  then  referenced  the  npm_package_config_port
       environment variable, then the user could override that by doing npm config  set  foo:port
       8001.

       See npm help 7 npm-config and npm help 7 npm-scripts for more on package configs.

dependencies

       Dependencies are specified in a simple object that maps a package name to a version range.
       The version range  is  a  string  which  has  one  or  more  space-separated  descriptors.
       Dependencies can also be identified with a tarball or git URL.

       Please  do  not  put  test  harnesses  or  transpilers  in  your dependencies object.  See
       devDependencies, below.

       See npm help 7 semver for more details about specifying version ranges.

       · version Must match version exactly

       · >version Must be greater than version

       · >=version etc

       · <version

       · <=version

       · ~version "Approximately equivalent to version"  See npm help 7 semver

       · ^version "Compatible with version"  See npm help 7 semver

       · 1.2.x 1.2.0, 1.2.1, etc., but not 1.3.0

       · http://... See 'URLs as Dependencies' below

       · * Matches any version

       · "" (just an empty string) Same as *

       · version1 - version2 Same as >=version1 <=version2.

       · range1 || range2 Passes if either range1 or range2 are satisfied.

       · git... See 'Git URLs as Dependencies' below

       · user/repo See 'GitHub URLs' below

       · tag A specific version tagged and published as tag  See npm help npm-dist-tag

       · path/path/path See Local Paths #local-paths below

       For example, these are all valid:

         { "dependencies" :
           { "foo" : "1.0.0 - 2.9999.9999"
           , "bar" : ">=1.0.2 <2.1.2"
           , "baz" : ">1.0.2 <=2.3.4"
           , "boo" : "2.0.1"
           , "qux" : "<1.0.0 || >=2.3.1 <2.4.5 || >=2.5.2 <3.0.0"
           , "asd" : "http://asdf.com/asdf.tar.gz"
           , "til" : "~1.2"
           , "elf" : "~1.2.3"
           , "two" : "2.x"
           , "thr" : "3.3.x"
           , "lat" : "latest"
           , "dyl" : "file:../dyl"
           }
         }

   URLs as Dependencies
       You may specify a tarball URL in place of a version range.

       This tarball will be downloaded and installed locally to your package at install time.

   Git URLs as Dependencies
       Git urls are of the form:

         <protocol>://[<user>[:<password>]@]<hostname>[:<port>][:][/]<path>[#<commit-ish> | #semver:<semver>]

       <protocol> is one of git, git+ssh, git+http, git+https, or git+file.

       If #<commit-ish> is provided, it will be  used  to  clone  exactly  that  commit.  If  the
       commit-ish  has  the  format  #semver:<semver>,  <semver> can be any valid semver range or
       exact version, and npm will look for any tags or refs matching that range  in  the  remote
       repository,  much  as  it  would  for  a  registry dependency. If neither #<commit-ish> or
       #semver:<semver> is specified, then master is used.

       Examples:

         git+ssh://git@github.com:npm/npm.git#v1.0.27
         git+ssh://git@github.com:npm/npm#semver:^5.0
         git+https://isaacs@github.com/npm/npm.git
         git://github.com/npm/npm.git#v1.0.27

   GitHub URLs
       As of version 1.1.65, you can refer to GitHub  urls  as  just  "foo":  "user/foo-project".
       Just as with git URLs, a commit-ish suffix can be included.  For example:

         {
           "name": "foo",
           "version": "0.0.0",
           "dependencies": {
             "express": "expressjs/express",
             "mocha": "mochajs/mocha#4727d357ea",
             "module": "user/repo#feature\/branch"
           }
         }

   Local Paths
       As  of  version 2.0.0 you can provide a path to a local directory that contains a package.
       Local paths can be saved using npm install -S or npm install --save, using  any  of  these
       forms:

         ../foo/bar
         ~/foo/bar
         ./foo/bar
         /foo/bar

       in  which  case they will be normalized to a relative path and added to your package.json.
       For example:

         {
           "name": "baz",
           "dependencies": {
             "bar": "file:../foo/bar"
           }
         }

       This feature is helpful for local offline development and creating tests that require  npm
       installing  where  you  don't  want to hit an external server, but should not be used when
       publishing packages to the public registry.

devDependencies

       If someone is planning on downloading and using your module in their  program,  then  they
       probably  don't  want  or  need  to  download and build the external test or documentation
       framework that you use.

       In this case, it's best to map these additional items in a devDependencies object.

       These things will be installed when doing npm link or npm  install  from  the  root  of  a
       package,  and  can  be  managed  like  any  other npm configuration param.  See npm help 7
       npm-config for more on the topic.

       For build steps that are not platform-specific, such as compiling  CoffeeScript  or  other
       languages  to JavaScript, use the prepare script to do this, and make the required package
       a devDependency.

       For example:

         { "name": "ethopia-waza",
           "description": "a delightfully fruity coffee varietal",
           "version": "1.2.3",
           "devDependencies": {
             "coffee-script": "~1.6.3"
           },
           "scripts": {
             "prepare": "coffee -o lib/ -c src/waza.coffee"
           },
           "main": "lib/waza.js"
         }

       The prepare script  will  be  run  before  publishing,  so  that  users  can  consume  the
       functionality  without  requiring them to compile it themselves.  In dev mode (ie, locally
       running npm install), it'll run this script as well, so that you can test it easily.

peerDependencies

       In some cases, you want to express the compatibility of your package with a host  tool  or
       library,  while not necessarily doing a require of this host.  This is usually referred to
       as a plugin. Notably, your module may be  exposing  a  specific  interface,  expected  and
       specified by the host documentation.

       For example:

         {
           "name": "tea-latte",
           "version": "1.3.5",
           "peerDependencies": {
             "tea": "2.x"
           }
         }

       This  ensures  your package tea-latte can be installed along with the second major version
       of the host package tea only. npm install tea-latte could  possibly  yield  the  following
       dependency graph:

         |-- tea-latte@1.3.5
         |-- tea@2.2.0

       NOTE:  npm  versions  1  and 2 will automatically install peerDependencies if they are not
       explicitly depended upon higher in the dependency tree. In the next major version  of  npm
       (npm@3),  this  will  no  longer  be  the  case.  You  will  receive  a  warning  that the
       peerDependency is not installed instead. The  behavior  in  npms  1  &  2  was  frequently
       confusing  and could easily put you into dependency hell, a situation that npm is designed
       to avoid as much as possible.

       Trying to install another plugin with a conflicting requirement will cause an  error.  For
       this reason, make sure your plugin requirement is as broad as possible, and not to lock it
       down to specific patch versions.

       Assuming the host complies with  semver  http://semver.org/,  only  changes  in  the  host
       package's  major  version  will  break  your plugin. Thus, if you've worked with every 1.x
       version of the host package, use "^1.0" or  "1.x"  to  express  this.  If  you  depend  on
       features introduced in 1.5.2, use ">= 1.5.2 < 2".

bundledDependencies

       This defines an array of package names that will be bundled when publishing the package.

       In  cases where you need to preserve npm packages locally or have them available through a
       single file download, you can bundle the packages in a  tarball  file  by  specifying  the
       package names in the bundledDependencies array and executing npm pack.

       For example:

       If we define a package.json like this:

         {
           "name": "awesome-web-framework",
           "version": "1.0.0",
           "bundledDependencies": [
             "renderized", "super-streams"
           ]
         }

       we  can  obtain  awesome-web-framework-1.0.0.tgz  file  by  running  npm  pack.  This file
       contains the dependencies renderized and super-streams which can be  installed  in  a  new
       project by executing npm install awesome-web-framework-1.0.0.tgz.

       If this is spelled "bundleDependencies", then that is also honored.

optionalDependencies

       If  a  dependency  can be used, but you would like npm to proceed if it cannot be found or
       fails to install, then you may put it in the optionalDependencies object.  This is  a  map
       of  package  name to version or url, just like the dependencies object.  The difference is
       that build failures do not cause installation to fail.

       It is still your program's responsibility to handle  the  lack  of  the  dependency.   For
       example, something like this:

         try {
           var foo = require('foo')
           var fooVersion = require('foo/package.json').version
         } catch (er) {
           foo = null
         }
         if ( notGoodFooVersion(fooVersion) ) {
           foo = null
         }

         // .. then later in your program ..

         if (foo) {
           foo.doFooThings()
         }

       Entries in optionalDependencies will override entries of the same name in dependencies, so
       it's usually best to only put in one place.

engines

       You can specify the version of node that your stuff works on:

         { "engines" : { "node" : ">=0.10.3 <0.12" } }

       And, like with dependencies, if you don't specify the version (or if you  specify  "*"  as
       the version), then any version of node will do.

       If  you specify an "engines" field, then npm will require that "node" be somewhere on that
       list. If "engines" is omitted, then npm will just assume that it works on node.

       You can also use the "engines" field to specify which  versions  of  npm  are  capable  of
       properly installing your program.  For example:

         { "engines" : { "npm" : "~1.0.20" } }

       Unless  the  user  has  set the engine-strict config flag, this field is advisory only and
       will only produce warnings when your package is installed as a dependency.

engineStrict

       This feature was removed in npm 3.0.0

       Prior to npm 3.0.0, this feature was used to treat this package as if  the  user  had  set
       engine-strict. It is no longer used.

os

       You can specify which operating systems your module will run on:

         "os" : [ "darwin", "linux" ]

       You  can  also  blacklist  instead  of  whitelist  operating  systems,  just  prepend  the
       blacklisted os with a '!':

         "os" : [ "!win32" ]

       The host operating system is determined by process.platform

       It is allowed to both blacklist, and whitelist, although there isn't any good reason to do
       this.

cpu

       If your code only runs on certain cpu architectures, you can specify which ones.

         "cpu" : [ "x64", "ia32" ]

       Like the os option, you can also blacklist architectures:

         "cpu" : [ "!arm", "!mips" ]

       The host architecture is determined by process.arch

preferGlobal

       DEPRECATED

       This option used to trigger an npm warning, but it will no longer warn. It is purely there
       for informational purposes. It is now recommended that you install any binaries  as  local
       devDependencies wherever possible.

private

       If you set "private": true in your package.json, then npm will refuse to publish it.

       This  is  a  way  to prevent accidental publication of private repositories.  If you would
       like to ensure that a given package is only ever published to  a  specific  registry  (for
       example,  an  internal registry), then use the publishConfig dictionary described below to
       override the registry config param at publish-time.

publishConfig

       This is a set of config values that will be used at publish-time. It's especially handy if
       you  want  to set the tag, registry or access, so that you can ensure that a given package
       is not tagged with "latest", published to the global public  registry  or  that  a  scoped
       module is private by default.

       Any  config  values  can  be overridden, but of course only "tag", "registry" and "access"
       probably matter for the purposes of publishing.

       See npm help 7 npm-config to see the list of config options that can be overridden.

DEFAULT VALUES

       npm will default some values based on package contents.

       · "scripts": {"start": "node server.js"} If there is a server.js file in the root of  your
         package, then npm will default the start command to node server.js.

       · "scripts":{"install":  "node-gyp rebuild"} If there is a binding.gyp file in the root of
         your package and you have not defined an install or preinstall script, npm will  default
         the install command to compile using node-gyp.

       · "contributors": [...]  If there is an AUTHORS file in the root of your package, npm will
         treat each line as a Name <email> (url) format, where email and url are optional.  Lines
         which start with a # or are blank, will be ignored.