Node.js - searching for the "util" module; identify core modules

Question

I'm really a big fan of Swagger's node module, but one thing is driving me crazy:

The sample app contains the following line (api/controller/hello_world.js):

var util = require('util');

But I just can't find this module. I tried to

• list it with npm list but nothing
• search for it with Spotlight (util.js)

My question is: How can I list the actually loaded modules in nodejs?

Answer 1

util is part of the node.js distribution: https://nodejs.org/api/util.html

Answer 2

TimWolla's answer solves your particular problem with respect to the util module.

As for the more generic question:

How can I list the actually loaded modules in nodejs?

• This answer tells you how to list the full filenames of currently loaded non-core modules (spoiler alert: Object.keys(require.cache).

• For core modules - modules that come with Node.js itself, such as util - there is no way that I know of that tells you which ones are loaded, but given that they're core, they may all implicitly be loaded, for all we know (and should care).

• That said, to test if a given module is a core module, you can use require.resolve(), which returns the input module name as-is (rather than a full filename) in the case of core modules; e.g.:

  require.resolve('util') // -> 'util', i.e. NOT A PATH -> core module
  

Note: When require.resolve() returns a filesystem path, the implication is merely that the module is non-core and can be located; it does not tell you whether or not that module is currently loaded (use require.cache for that).