Private repo dependency installs but "Cannot Find Module" - node.js

Question

I have a project that requires a private repo as a dependency. So, projectA has this included in the package.json as "projectB": "user/repo". This installs just fine, and is listed in projectA node_modules. The problem is, that node throws and error where I require the functions of the dependency. The error being that "Cannot find module projectB". As mentioned, projectB is listed in node_modules. Here is the structure of projectB:
.
├── README.md
├── file1.js
├── file2.js
├── file3.js
├── file4.js
└── package.json
It also has its own node_modules, but I've left that out. Now, here is what file1.js might look like:
function getResult (a, b) {
return a + b;
}
module.exports = { getResult }
And here is what projectA looks like:
var calculate = require('projectB').file1.getResult; // I've tried this in several other ways too
Calling calculate results in the "Cannot find module error". Have I done something fundamentally wrong in setting up for using a private repo as dependency and/or requiring it wrong?
Update projectB package.json
{
"name": "projectB",
"version": "1.0.0",
"description": "Backend utility functions",
"scripts": {
"test": "mocha"
},
"repository": {
"type": "git",
"url": "git+https://github.com/user/repo.git"
},
"author": "Me",
"license": "ISC",
"bugs": {
"url": "https://github.com//user/repo/issues"
},
"homepage": "https://github.com//user/repo#readme",
"dependencies": {
"lodash": "^4.17.4",
"mongodb": "^2.2.25",
"redis": "^2.7.1",
"winston": "^2.3.1"
}
}

Answer 1

projectB needs to be updated to set an appropriate main, but by default this will be index.js. You could do something like the following:
// projectB/index.js
exports.file1 = require("./file1");
exports.file2 = require("./file2");
exports.file3 = require("./file3");
exports.file4 = require("./file4");
It's actually a pretty common pattern to have an index.js that does nothing but export from library files.