Module
Global Description
tls
No
Transport Layer Security (TLS) communication utilities.
tty
No
Low-level TeleTYpewriter (TTY) functions.
dgram
No
User Datagram Protocol (UDP) networking utilities.
url
Yes
URL prasing utilities.
util
No
Internal Node utilities.
vm
No
Virtual (JavaScript) Machine: allows for metaprogramming and context creation.
zlib
No
Compression utilities.
It is beyond the scope of this book to cover all of these modules (we will discuss the
most important ones in this chapter), but this list gives you a starting point to look
for more information. Detailed documentation for these modules is available in the
Finally, there are npm modules. npm modules are file modules with a specific naming
convention. If you require some module
x
(where
x
is not a core module), Node will
look in the current directory for a subdirectory called node_modules. If it finds it, it
will look for
x
in that directory. If it doesn’t find it, it will go up to the parent direc‐
tory, look for a module called node_modules there, and repeat the process until it
finds the module or reaches the root. For example, if your project is located in /home/
jdoe/test_project, and in your application file, you call
require('x')
, Node will look
for the module
x
in the following locations (in this order):
•
/home/jdoe/test_project/node_modules/x
•
/home/jdoe/node_modules/x
•
/home/node_modules/x
•
/node_modules/x
For most projects, you’ll have a single node_modules directory in the application root.
Furthermore, you shouldn’t add or remove things from that directory manually;
you’ll let npm do all the heavy lifting. Still, it’s useful to know how Node resolves
module imports, especially when it comes time to debug problems in third-party
modules.
For modules that you write yourself, do not put them in node_modules. It will work,
but the point of node_modules is that it’s a directory that can be deleted at any time
and re-created by npm from the dependencies listed in package.json (see
286 | Chapter 20: Node
