How do you import a function with parameters using ECMAScrip6?

Question

I am setting up a brand new project in Express using Babel and ESLint, and am trying to setup dynamic routes. The only issue is that I cannot figure out how to call the loader for the routes. This is my current code regarding the loader.

routes/index.js

import fs from 'fs';

/**
 * Register Default Routes
 * @param {Object} app express.Application
 */
export default function(app) {
    fs.readdirSync(__dirname).forEach((fileName) => {
        if (fileName == __filename.slice(__dirname.length + 1)) return;
        let fileNameStripped = fileName.substring(0, fileName.lastIndexOf('.'));
        require('./' + fileNameStripped)(app); // does not work
    });
}

index.js

import express from 'express';
import routes from './routes/index.js';

const app = express();

app.use(express.static('public'));

routes(app); // works now

...

Babel Error

TypeError: require(...) is not a function
    at /app/build/routes/index.js:1:314
    at Array.forEach (<anonymous>)
    at exports.default (/app/build/routes/index.js:1:195)
    at Object.<anonymous> (/app/build/index.js:1:393)    
    at Module._compile (module.js:649:30)
    at Object.Module._extensions..js (module.js:660:10)
    at Module.load (module.js:561:32)
    at tryModuleLoad (module.js:501:12)
    at Function.Module._load (module.js:493:3)
    at Function.Module.runMain (module.js:690:10)

The issue appears to be related to https://github.com/babel/babel/issues/2683

This was based off of https://stackoverflow.com/questions/29923879/pass-options-to-es6-module-imports, although it did not work. — , Mar 19 '18 at 12:45
It's unclear what the problem is. Does the code above not work for you, and if it doesn't, what's wrong with it? I don't see why it's important that it's an import. It's a function that can accept an argument, imported or not. — Estus Flask, Mar 19 '18 at 12:48
This issue is that the function is not called, the one in routes/index.js and index.js — , Mar 19 '18 at 12:50
Well, it should, because you call it. If there are problems, there should be errors. Currently nobody but you can debug it. Consider providing http://stackoverflow.com/help/mcve that can replicate the problem - a repo, online service or else. Otherwise the question is considered off-topic. — Estus Flask, Mar 19 '18 at 13:02
You haven't posted nested route files. But I guess they use ES module `default` exports too, so `require('./' + fileNameStripped)` is module object, and it should be `require('./' + fileNameStripped).default(app)`. — Estus Flask, Mar 19 '18 at 14:07
Thanks @estus, can you create a answer with the content from the comment above this as it solved my issue. — , Mar 19 '18 at 14:53

score 0 · Accepted Answer · answered Mar 19 '18 at 15:09

Since nested route files are supposed to be ES modules with default exports, require('./' + fileNameStripped) is module object and not a function. It should be:

require('./' + fileNameStripped).default(app);

Depending on Babel configuration (dynamic-import-node plugin is required), require() can be replaced with dynamic import() but it's less desirable here, because dynamic import is not synchronous and can cause race conditions.

How do you import a function with parameters using ECMAScrip6?

1 Answers1