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.TH "NPM\-FOLDERS" "5" "August 2018" "" ""
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.SH "NAME"
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\fBnpm-folders\fR \- Folder Structures Used by npm
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.SH DESCRIPTION
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.P
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npm puts various things on your computer\. That's its job\.
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.P
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This document will tell you what it puts where\.
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.SS tl;dr
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.RS 0
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.IP \(bu 2
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Local install (default): puts stuff in \fB\|\./node_modules\fP of the current
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package root\.
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.IP \(bu 2
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Global install (with \fB\-g\fP): puts stuff in /usr/local or wherever node
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is installed\.
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.IP \(bu 2
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Install it \fBlocally\fR if you're going to \fBrequire()\fP it\.
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.IP \(bu 2
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Install it \fBglobally\fR if you're going to run it on the command line\.
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.IP \(bu 2
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If you need both, then install it in both places, or use \fBnpm link\fP\|\.
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.RE
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.SS prefix Configuration
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.P
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The \fBprefix\fP config defaults to the location where node is installed\.
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On most systems, this is \fB/usr/local\fP\|\. On Windows, it's \fB%AppData%\\npm\fP\|\.
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On Unix systems, it's one level up, since node is typically installed at
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\fB{prefix}/bin/node\fP rather than \fB{prefix}/node\.exe\fP\|\.
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.P
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When the \fBglobal\fP flag is set, npm installs things into this prefix\.
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When it is not set, it uses the root of the current package, or the
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current working directory if not in a package already\.
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.SS Node Modules
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.P
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Packages are dropped into the \fBnode_modules\fP folder under the \fBprefix\fP\|\.
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When installing locally, this means that you can
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\fBrequire("packagename")\fP to load its main module, or
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\fBrequire("packagename/lib/path/to/sub/module")\fP to load other modules\.
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.P
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Global installs on Unix systems go to \fB{prefix}/lib/node_modules\fP\|\.
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Global installs on Windows go to \fB{prefix}/node_modules\fP (that is, no
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\fBlib\fP folder\.)
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.P
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Scoped packages are installed the same way, except they are grouped together
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in a sub\-folder of the relevant \fBnode_modules\fP folder with the name of that
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scope prefix by the @ symbol, e\.g\. \fBnpm install @myorg/package\fP would place
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the package in \fB{prefix}/node_modules/@myorg/package\fP\|\. See npm help 7 \fBscope\fP for
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more details\.
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.P
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If you wish to \fBrequire()\fP a package, then install it locally\.
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.SS Executables
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.P
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When in global mode, executables are linked into \fB{prefix}/bin\fP on Unix,
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or directly into \fB{prefix}\fP on Windows\.
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.P
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When in local mode, executables are linked into
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\fB\|\./node_modules/\.bin\fP so that they can be made available to scripts run
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through npm\. (For example, so that a test runner will be in the path
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when you run \fBnpm test\fP\|\.)
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.SS Man Pages
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.P
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When in global mode, man pages are linked into \fB{prefix}/share/man\fP\|\.
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.P
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When in local mode, man pages are not installed\.
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.P
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Man pages are not installed on Windows systems\.
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.SS Cache
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.P
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See npm help \fBnpm\-cache\fP\|\. Cache files are stored in \fB~/\.npm\fP on Posix, or
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\fB%AppData%/npm\-cache\fP on Windows\.
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.P
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This is controlled by the \fBcache\fP configuration param\.
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.SS Temp Files
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.P
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Temporary files are stored by default in the folder specified by the
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\fBtmp\fP config, which defaults to the TMPDIR, TMP, or TEMP environment
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variables, or \fB/tmp\fP on Unix and \fBc:\\windows\\temp\fP on Windows\.
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.P
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Temp files are given a unique folder under this root for each run of the
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program, and are deleted upon successful exit\.
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.SH More Information
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.P
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When installing locally, npm first tries to find an appropriate
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\fBprefix\fP folder\. This is so that \fBnpm install foo@1\.2\.3\fP will install
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to the sensible root of your package, even if you happen to have \fBcd\fPed
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into some other folder\.
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.P
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Starting at the $PWD, npm will walk up the folder tree checking for a
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folder that contains either a \fBpackage\.json\fP file, or a \fBnode_modules\fP
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folder\. If such a thing is found, then that is treated as the effective
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"current directory" for the purpose of running npm commands\. (This
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behavior is inspired by and similar to git's \.git\-folder seeking
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logic when running git commands in a working dir\.)
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.P
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If no package root is found, then the current folder is used\.
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.P
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When you run \fBnpm install foo@1\.2\.3\fP, then the package is loaded into
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the cache, and then unpacked into \fB\|\./node_modules/foo\fP\|\. Then, any of
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foo's dependencies are similarly unpacked into
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\fB\|\./node_modules/foo/node_modules/\.\.\.\fP\|\.
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.P
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Any bin files are symlinked to \fB\|\./node_modules/\.bin/\fP, so that they may
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be found by npm scripts when necessary\.
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.SS Global Installation
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.P
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If the \fBglobal\fP configuration is set to true, then npm will
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install packages "globally"\.
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.P
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For global installation, packages are installed roughly the same way,
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but using the folders described above\.
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.SS Cycles, Conflicts, and Folder Parsimony
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.P
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Cycles are handled using the property of node's module system that it
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walks up the directories looking for \fBnode_modules\fP folders\. So, at every
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stage, if a package is already installed in an ancestor \fBnode_modules\fP
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folder, then it is not installed at the current location\.
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.P
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Consider the case above, where \fBfoo \-> bar \-> baz\fP\|\. Imagine if, in
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addition to that, baz depended on bar, so you'd have:
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\fBfoo \-> bar \-> baz \-> bar \-> baz \.\.\.\fP\|\. However, since the folder
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structure is: \fBfoo/node_modules/bar/node_modules/baz\fP, there's no need to
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put another copy of bar into \fB\|\.\.\./baz/node_modules\fP, since when it calls
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require("bar"), it will get the copy that is installed in
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\fBfoo/node_modules/bar\fP\|\.
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.P
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This shortcut is only used if the exact same
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version would be installed in multiple nested \fBnode_modules\fP folders\. It
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is still possible to have \fBa/node_modules/b/node_modules/a\fP if the two
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"a" packages are different versions\. However, without repeating the
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exact same package multiple times, an infinite regress will always be
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prevented\.
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.P
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Another optimization can be made by installing dependencies at the
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highest level possible, below the localized "target" folder\.
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.SS Example
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.P
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Consider this dependency graph:
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.P
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.RS 2
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.nf
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foo
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+\-\- blerg@1\.2\.5
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+\-\- bar@1\.2\.3
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| +\-\- blerg@1\.x (latest=1\.3\.7)
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| +\-\- baz@2\.x
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| | `\-\- quux@3\.x
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| | `\-\- bar@1\.2\.3 (cycle)
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| `\-\- asdf@*
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`\-\- baz@1\.2\.3
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`\-\- quux@3\.x
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`\-\- bar
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.fi
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.RE
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.P
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In this case, we might expect a folder structure like this:
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.P
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.RS 2
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.nf
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foo
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+\-\- node_modules
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+\-\- blerg (1\.2\.5) <\-\-\-[A]
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+\-\- bar (1\.2\.3) <\-\-\-[B]
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| `\-\- node_modules
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| +\-\- baz (2\.0\.2) <\-\-\-[C]
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| | `\-\- node_modules
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| | `\-\- quux (3\.2\.0)
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| `\-\- asdf (2\.3\.4)
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`\-\- baz (1\.2\.3) <\-\-\-[D]
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`\-\- node_modules
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`\-\- quux (3\.2\.0) <\-\-\-[E]
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.fi
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.RE
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.P
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Since foo depends directly on \fBand\fP\fB, those are
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installed in foo's\fPnode_modules` folder\.
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.P
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Even though the latest copy of blerg is 1\.3\.7, foo has a specific
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dependency on version 1\.2\.5\. So, that gets installed at [A]\. Since the
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parent installation of blerg satisfies bar's dependency on `,
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it does not install another copy under [B]\.
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.P
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Bar [B] also has dependencies on baz and asdf, so those are installed in
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bar's \fBnode_modules\fP folder\. Because it depends on \fB, it cannot
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re\-use the\fP\fBinstalled in the parent\fPnode_modules` folder [D],
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and must install its own copy [C]\.
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.P
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Underneath bar, the \fBbaz \-> quux \-> bar\fP dependency creates a cycle\.
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However, because bar is already in quux's ancestry [B], it does not
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unpack another copy of bar into that folder\.
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.P
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Underneath \fBfoo \-> baz\fP [D], quux's [E] folder tree is empty, because its
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dependency on bar is satisfied by the parent folder copy installed at [B]\.
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.P
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For a graphical breakdown of what is installed where, use \fBnpm ls\fP\|\.
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.SS Publishing
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.P
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Upon publishing, npm will look in the \fBnode_modules\fP folder\. If any of
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the items there are not in the \fBbundledDependencies\fP array, then they will
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not be included in the package tarball\.
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.P
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This allows a package maintainer to install all of their dependencies
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(and dev dependencies) locally, but only re\-publish those items that
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cannot be found elsewhere\. See npm help 5 \fBpackage\.json\fP for more information\.
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.SH SEE ALSO
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.RS 0
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.IP \(bu 2
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npm help 5 package\.json
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.IP \(bu 2
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npm help install
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.IP \(bu 2
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npm help pack
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.IP \(bu 2
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npm help cache
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.IP \(bu 2
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npm help config
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.IP \(bu 2
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npm help 5 npmrc
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.IP \(bu 2
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npm help 7 config
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.IP \(bu 2
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npm help publish
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.RE
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