One of the key steps in becoming immersed in an ecosystem is learning its vocabulary. Node.js and npm have very specific definitions of packages and modules, which are easy to mix up. We'll discuss those definitions here, make them distinct, and explain why certain default files are named the way they are.
package.json.
This can happen in a bunch of different ways! For more info, see
"What is a package?, below.require(). Again, there are several configurations that allow this to
happen. For more info, see "What is a module?", below.package?A package is any of:
package.json file<name>@<version> that is published on the registry with (c)<name>@<tag> that points to (d)<name> that has a latest tag satisfying (e)git url that, when cloned, results in (a).Noting all these package possibilities, it follows that even if you never
publish your package to the public registry, you can still get a lot of
benefits of using npm:
Git urls can be of the form:
git://github.com/user/project.git#commit-ishgit+ssh://user@hostname:project.git#commit-ishgit+http://user@hostname/project/blah.git#commit-ishgit+https://user@hostname/project/blah.git#commit-ish
The commit-ish can be any tag, sha, or branch which can be supplied as
an argument to git checkout. The default is master.
module?A module is anything that can be loaded with require() in a Node.js
program. The following are all examples of things that can be
loaded as modules:
package.json file containing a main field.index.js file in it.Generally, npm packages that are used in Node.js program are loaded
with require, making them modules. However, there's no requirement
that an npm package be a module!
Some packages, e.g., cli packages only contain an executable
command-line interface, and don't provide a main field for use in
Node.js programs. These packages are not modules.
Almost all npm packages (at least, those that are Node programs)
contain many modules within them (because every file they load with
require() is a module).
In the context of a Node program, the module is also the thing that
was loaded from a file. For example, in the following program:
var req = require('request')
we might say that "The variable req refers to the request module".
node_modules folder, but package.json file?node_packages or module.json?The package.json file defines the package. (See
"What is a package?", above.)
The node_modules folder is the place Node.js looks for modules.
(See "What is a module?", above.)
For example, if you create a file at node_modules/foo.js and then
had a program that did var f = require('foo.js'), it would load
the module. However, foo.js is not a "package" in this case,
because it does not have a package.json.
Alternatively, if you create a package which does not have an
index.js or a "main" field in the package.json file, then it is
not a module. Even if it's installed in node_modules, it can't be
an argument to require().
Last modified February 11, 2016 Found a typo? Send a pull request!