[nodejs] Conceptual question about modules [learnyounode: Make It Modular]

Simon Renoult

2018-08-07 09:17:04 UTC

Hi Matias,

It's mostly a question of definition:

A *module* is a file (see the official documentation
<https://nodejs.org/api/modules.html#modules_modules>). A *module* (ie: a
file) can export anything from a variable to a function. If it starts with
"./" (ie: "require('./foo')") Node.js will try to find it based on its
relative path. If it's just the package name (ie: "require('path')"),
Node.js will try to find it in its native modules (http, fs, etc.) or in
your local installed modules (in "node_modules").

So if you want to create a new module named "mod1", you have two options:

- Simple solution: create a file named "mod1.js". Don't forget to
prepend "./" when requiring the file: "require('./mod1.js');". The file
extension ".js" can be omitted.
- Complicated solution: publish an npm package
<https://docs.npmjs.com/getting-started/publishing-npm-packages>.

To answer your questions:

I would have to create a subfolder named "mod1" with files *index.js* and

Post by Matias Salimbene
*package.json*. Does *index.js* contains the actual code, and
*package.json* is simply descriptive?

No. This is only necessary when creating an npm package (aka the
"Complicated solution").

The workshop doesn't seem to use said structure but instead simple uses a

Post by Matias Salimbene
separate file for the *exported function* code. I think it has to do with
using a *single function export*, rather that a full module that would
contain any amount of function (I guess).

No. A module can contain as many functions as you want. And a *module *can
be made of *modules*, so it scales. But it's mostly a matter of definition.
In Node.js a *module* is just a file. You could consider that what *you*
call *module* is what we usually call a *pacakge*. A *package* can be found
on NPM (= Node *Package* Manager). A *package* is not an official Node.js
term though. A *package* is a module (aka a JavaScript file) + a
package.json file that describes this module dependencies and other meta
information.

Even though I've created the subfolder with both files, when i ran the
node -pe "require('mod1')"
I get

Post by Matias Salimbene
Error: Cannot find module 'mod1' error.

Yep, you forgot "./" "before "mod1".

Post by Matias Salimbene
Hello there, I'm going through the learnyounode workshop, currently on the
Make It Modular section. I'm not getting a clear picture of how modules
work.
-
I would have to create a subfolder named "mod1" with files *index.js*
and *package.json*. Does *index.js* contains the actual code, and
*package.json* is simply descriptive?
-
The workshop doesn't seem to use said structure but instead simple
uses a separate file for the *exported function* code. I think it has
to do with using a *single function export*, rather that a full module
that would contain any amount of function (I guess).
-
Even though I've created the subfolder with both files, when i ran the
node -pe "require('mod1')"
I get
Error: Cannot find module 'mod1' error.
Any clarification to these is greatly appreciated, cheers!

--
Job board: http://jobs.nodejs.org/
New group rules: https://gist.github.com/othiym23/9886289#file-moderation-policy-md
Old group rules: https://github.com/joyent/node/wiki/Mailing-List-Posting-Guidelines
---
You received this message because you are subscribed to the Google Groups "nodejs" group.
To unsubscribe from this group and stop receiving emails from it, send an email to nodejs+***@googlegroups.com.
To post to this group, send email to ***@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/nodejs/692cb737-0397-404b-ac0b-fc171df5c8e4%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.