Check if a node.js module is available

Question

I'm looking for a way to find out if a module is available.

For example, I want to check if the module mongodb is available, programmatically.

Also, it shouldn't halt the program if a module isn't found, I want to handle this myself.

_{PS: I added this question because Google isn't helpful.}

score 30 · Accepted Answer · answered Oct 11 '15 at 17:28

There is a more clever way if you only want to check whether a module is available (but not load it if it's not):

function moduleAvailable(name) {
    try {
        require.resolve(name);
        return true;
    } catch(e){}
    return false;
}

if (moduleAvailable('mongodb')) {
    // yeah we've got it!
}

score 16 · Answer 2 · answered Jul 22 '12 at 13:31

16

Here is the most clever way I found to do this. If anyone has a better way to do so, please point it out.

var mongodb;
try {
    mongodb = require( 'mongodb' );
}
catch( e ) {
    if ( e.code === 'MODULE_NOT_FOUND' ) {
        // The module hasn't been found
    }
}

answered Jul 22 '12 at 13:31

Florian Margaine

58,730
15
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5

Be careful using this with your own modules. `MODULE_NOT_FOUND` will be called if a nested require fails. To avoid this a regex could be used on the message to check which module was not found. It would be advisable to print the actual error message to the console. Using `require.resolve` first would avoid this too. – vaughan Jan 14 '14 at 01:11
Wouldn't this be better if it were to rethrow the error if it isn't MODULE_NOT_FOUND? – Jasper Jan 18 '19 at 18:04

score 1 · Answer 3 · answered Jun 15 '22 at 09:56

For ECMAScript modules (ESM) since Node 12 the import keyword can also be used as function that returns a Promise:

import("mongodb")
  .then(mongodb => {
    // use module
  })
  .catch(e => console.error(e)) // The module hasn't been found

or

async main() {
  const mongodb = import("mongodb")
  // use module
}

main().catch(e => console.error(e)) // module hasn't been found or other error

score 0 · Answer 4 · answered Apr 22 '16 at 11:27

Maybe resolve-like modules will be helpfully here?

The numbers of modules are exist on npm:

I wrote first, async-resolve, and for example:

var Resolver = require('async-resolve');
var resolver_obj = new Resolver();
resolver_obj.resolve('module', __dirname, function(err, filename) {
  return console.log(filename);
});

It use node modules path resolutions rules but don't block main loop as node do it. And in result you get filename, so it can be used to decide its local module or global and other things.

codeNinja · Answer 5 · 2017-06-07T08:12:17.200

0

ES6 simple solution with 1 line of code :

const path = require('path');
const fs = require('fs');

function hasDependency(dep) {
        return module.paths.some(modulesPath => fs.existsSync(path.join(modulesPath, dep)));
}

edited Jun 07 '17 at 08:12

answered Jun 05 '17 at 22:46

codeNinja

1
1

4

Please explain your answer with some code comments or some descriptive text in the answer. A lot of skill levels will find this and it can be easier to sue if it is explained. – Brody Jun 06 '17 at 00:38

pravdomil · Answer 6 · 2016-04-07T15:32:10.563

-9

using ES6 arrow functions

var modulePath = m => { try { return require.resolve(m) } catch(e) { return false } }

edited Apr 07 '16 at 15:32

answered Mar 12 '16 at 19:20

pravdomil

2,961
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38

4

What's the advantage of using ES6 arrow functions? Is it worth answering a 3 years old question for this? – Florian Margaine Mar 12 '16 at 20:28
1

@Florian Margaine the advantage of arrow functions is that all work can be done in one line – pravdomil Apr 06 '16 at 14:22
4

that's not an advantage when you have a try/catch on a single line. Never do that. Seriously. – Florian Margaine Apr 06 '16 at 16:15
@Florian Margaine what about now? – pravdomil Apr 07 '16 at 12:23
5

then there is no advantage to using arrow function. – Florian Margaine Apr 07 '16 at 13:07

Check if a node.js module is available

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