Does having the same `require` in multiple files increase runtime

Question

So I'm planning to separate my functions into separate files and then import them into a single index.js which then becomes the main exporter. So I'm wondering if having something like var bcrypt = require('bcrypt') in several of my files be slower than just having it in one file.

Here's how I'm planning to group and export in index.js

const fs = require('fs');
const path = require('path')
const modules = {}

const files = fs.readdirSync(__dirname)
files.forEach(file => {
    if (file === 'index.js') return
    let temp = require(path.join(__dirname, file))

    for (let key in temp) {
        modules[key] = temp[key]
    }
});
module.exports = modules

As an example of what I mean:

file1.js

var bcrypt = require("bcrypt");

module.exports.file1test = "hi"

file2.js

var bcrypt = require("bcrypt");

module.exports.file2test = "bye"

Answer 1

No, it does not. Whenever a module is required for the first time, the module's code runs, assigns something to its exports, and those exports are returned. Further requires of that module simply reference those exports again. The logic is similar to this:

const importModule = (() => {
  const exports = {};
  return (name) => {
    if (!exports[name]) exports[name] = runModule(name);
    return exports[name];
  };
})();

So, multiple imports of the same module is no more expensive than referencing an object multiple times.