Logic to implement get list, get, post, put and delete. This one is done without promises. Logic is generic so can be used with any mongoose model

crud-with-mongodb-and-node-v8-without-promises.js

'use strict';

require('./model');
const mongoose = require('mongoose');
const Model = mongoose.model('Rep');
const _ = require('lodash');


const controller = {
    
    list: (req, res) => {
        Model.find(getCallback(opTypes.list, req, res));
    },

    get: (req, res) => {
        Model.findById(_.get(req, 'params.id')).exec(getCallback(opTypes.get, req, res));
    },

    post: (req, res) => {
        const data = _.pick(req.body, _.pickSchema(Model));
        new Model(data).save(getCallback(opTypes.post, req, res));
    },

    put: (req, res) => {
        Model.findById(_.get(req, 'params.id')).exec(getCallback(opTypes.put, req, res));  
    },

    delete: (req, res) => {
        Model.findById(_.get(req, 'params.id')).exec(getCallback(opTypes.delete, req, res));
    }
};

const getTypeResponse = (res, result) => res.json(result);
const saveTypeResponse = (res, result) => res.send(result._id);
const deleteTypeResponse = (res, result) => res.send('Delete Successful');

const handleSuccess = (opType, req, res, result) => {
    console.log(opType.text + ' successfull', result);
    opType.response(res, result);
};

const reportFailure = (opType, res, err, statusCode) => {
    console.log(opType.text + ' failed: ', err);
    res.status(statusCode || opType.errorStatusCode).send({error: opType.text +' failed'});
};

const handleOpStatus = (opType, req, res, err, result, statusCode) => {
    if(err){
        reportFailure(opType, res, err, statusCode);
    } else {
       handleSuccess(opType, req, res, result);
    }
};

const putOp = (opType, req, res, result) => {
    var body = _.get(req, 'body');
    const validKeys = _.intersection(_.keys(body), _.pickSchema(Model))
    const data = _.pick(body, validKeys);

    _.extend(result, data);
    result.save(handleOpStatus(opTypes.put, req, res, null, result));
};

const deleteOp = (opType, req, res, result) => {
    result.remove(handleOpStatus(opTypes.delete, req, res, null, result));
};

const opTypes = {
    list: { emptyAllowed: true, text: 'Get list', response: getTypeResponse, errorStatusCode: 404, op: handleSuccess }, 
    get: { text: 'Get', response: getTypeResponse, errorStatusCode: 404, op: handleSuccess }, 
    post: { text: 'Save', response: saveTypeResponse, errorStatusCode: 500, op: handleSuccess },
    put: { text: 'Update', response: saveTypeResponse, errorStatusCode: 500, op: putOp },
    delete: { text: 'Delete', response: deleteTypeResponse, errorStatusCode: 500, op: deleteOp }
};

const getCallback = (opType, req, res) => {
    return (err, result) => {
        if(err){
            reportFailure(opType, res, err);
        } else {
            if(!result && !opType.emptyAllowed){
                reportFailure(opType, res, 'Not Found', 404)
            } else {
                opType.op(opType, req, res, result);
            }
        }
    };  
};

module.exports = controller;