Q: How to get Mern Stack to work on Heroku I'm testing out the Mern Stack (Mongo Express React/Redux Node) and set it up with development with no issue. Now I'm trying to deploy to Heroku. I did a git push heroku master just like normal, but when I check out the website I see Heroku's Application Error. I added a MongoDB through Heroku, and changed my heroku config variables, so it uses that db (I think I did this correctly). So I check into logs:
npm ERR! file sh
npm ERR! code ELIFECYCLE
npm ERR! errno ENOENT
npm ERR! syscall spawn
npm ERR! mern-starter@1.0.0 start: `cross-env NODE_ENV=development nodemon index.js`
npm ERR! spawn ENOENT

A little way down:
 > mern-starter@1.0.0 start /app
 > cross-env NODE_ENV=development nodemon index.js
   sh: 1: cross-env: not found

Further down:
npm ERR! Linux 3.13.0-79-generic
npm ERR! argv "/app/.heroku/node/bin/node" "/app/.heroku/node/bin/npm" "start"
npm ERR! node v5.10.0
npm ERR! npm  v3.8.3
npm ERR! file sh
npm ERR! code ELIFECYCLE
npm ERR! errno ENOENT
npm ERR! mern-starter@1.0.0 start: `cross-env NODE_ENV=development nodemon index.js`
npm ERR! syscall spawn
npm ERR! spawn ENOENT
npm ERR!
npm ERR! Failed at the mern-starter@1.0.0 start script 'cross-env NODE_ENV=development nodemon index.js'.

So I don't know as much about the back end, but it appears to be running the development script in package.json:
"scripts": {
    "test": "mocha shared/tests/*.spec.js --compilers js:babel-register",
    "test:server": "cross-env NODE_ENV=test PORT=8080 MONGO_URL=mongodb://localhost:27017/mern-test mocha --compilers js:babel-register --recursive server/tests/**/*.spec.js",
    "start": "cross-env NODE_ENV=development nodemon index.js",
    "start:prod": "cross-env NODE_ENV=production node index.js",
    "bs": "npm run clean && npm run build && npm run start:prod",
    "minify": "cleancss -o static/css/app.min.css static/css/app.css",
    "build": "cross-env NODE_ENV=production webpack --config webpack.config.prod.js && npm run minify",
    "clean": "rimraf static/dist",
    "slate": "rimraf node_modules && npm install",
    "lint": "eslint client server shared"
  }

So how can I get this to work?
EDIT:
"devDependencies": {
    "babel-eslint": "^5.0.0-beta6",
    "babel-loader": "^6.2.1",
    "babel-plugin-react-transform": "^2.0.0",
    "babel-plugin-transform-react-constant-elements": "6.5.0",
    "babel-plugin-transform-react-inline-elements": "6.6.5",
    "babel-plugin-transform-react-remove-prop-types": "0.2.4",
    "babel-polyfill": "^6.3.14",
    "babel-preset-es2015": "^6.3.13",
    "babel-preset-react": "^6.3.13",
    "babel-preset-react-hmre": "^1.1.0",
    "babel-register": "^6.7.2",
    "chai": "^3.5.0",
    "clean-css": "^3.4.9",
    "cross-env": "^1.0.7",
    "css-loader": "^0.23.1",
    "css-modules-require-hook": "^2.1.0",
    "deep-freeze": "0.0.1",
    "eslint": "^1.10.3",
    "eslint-config-airbnb": "^4.0.0",
    "eslint-plugin-react": "^3.16.1",
    "expect": "^1.13.4",
    "expect-jsx": "^2.2.2",
    "extract-text-webpack-plugin": "^1.0.1",
    "mocha": "^2.4.5",
    "nodemon": "^1.9.1",
    "pre-commit": "^1.1.2",
    "react-addons-test-utils": "^0.14.7",
    "react-transform-hmr": "^1.0.1",
    "redux-devtools": "^3.1.1",
    "redux-devtools-dock-monitor": "^1.1.0",
    "redux-devtools-log-monitor": "^1.0.4",
    "rimraf": "^2.5.1",
    "style-loader": "^0.13.0",
    "supertest": "^1.1.0",
    "webpack": "^1.12.12",
    "webpack-dev-middleware": "^1.5.1",
    "webpack-hot-middleware": "^2.6.4"
  },


A: I wrote about it here: https://hashnode.com/post/deploying-mern-to-heroku-success-cio7sc1py013nis531rg3lfmz
The reason is because herokou does not know about your devDependencies tree, only your regular dependencies get pushed.
A quick fix is to copy all of your devDependencies to your dependencies
You will also have to remove the following from the .gitignore file:

public/*
static/dist
static/css/app.min.css

There are a couple other steps I outlined in the article, but those are the primary reasons it won't work without some extra configurations.
