This sounds to me as though your partner forgot to add dependencies to the package.json file. Also your partner might have a different Node.JS major version. You should talk to them and define a version you will also use in production. You should both work with the same version.
btw, you can just use a "local" strict mode, so you won't have problems with external dependencies:
'use strict';
module.exports = function() {
// implementation
};