PJC-1 / M.E.R.N.-back-end-

M.E.R.N. (back end)

Building a basic MERN stack application. Following Krunal Lathiya's MERN Stack Tutorial.

This repository will contain the Express.js back-end, which will communicate with our React.js front-end.

The following are notes from documentation, articles, and personal observations/opinions regarding building a MERN stack application and deploying it.

Helpful Links

Node.js CORS middleware

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Node.js

process.exit()

The process.exit() method instructs node.js to terminate the process synchronously with an exit status of code. If code is omitted, exit uses either the 'success' code 0 or the value of process.exitCode if it has been set. Node.js will not terminate until all the exit event listeners are called.

process.exit(1) to exit with a failure code.

Link to more information on process.exit() at the Node.js documentation.

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Heroku

Error: Cannot find module 'cli-engine'

preparation

To set up your application for deployment, you need to add the port environment variable that will be used by heroku into your main server file.

// example main server file

app.listen(process.env.PORT || 3000, function(){
  console.log('now listening to smooth sounds of port 3000...');
});

Second, you need to specify the "start" script command in the package.json file.

// example package.json file

{
  "name": "example",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "node index.js"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "express": "^4.16.2"
  }
}

Saw this error immediately after attempting to execute heroku create

module.js:491
    throw err;
    ^
Error: Cannot find module 'cli-engine'
    at Function.Module._resolveFilename (module.js:489:15)
    at Function.Module._load (module.js:439:25)
    at Module.require (module.js:517:17)
    at require (internal/module.js:11:18)
    at Object.<anonymous> (/Users/example/.local/share/heroku/client/bin/heroku.js:2:13)
    at Module._compile (module.js:573:30)
    at Object.Module._extensions..js (module.js:584:10)
    at Module.load (module.js:507:32)
    at tryModuleLoad (module.js:470:12)
    at Function.Module._load (module.js:462:3)

Was resolved by uninstalling and reinstalling heroku

brew uninstall --force heroku
brew install heroku

Link to a stackoverflow about an issue with this error message.

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mLab

Remember to create a database user for the database you create on mLab. The database user will be used with the MongoDB URI, which is used for connecting with your mongo database.

mongodb://<dbuser>:<dbpassword>@bd12345.mlab.com:12345/exampledb

Remember to add this to your code that is initializing the connection to the mongo database.

mongoose.connect(process.env.MONGODB_URI || 'mongodb://localhost/example');

Also add the MONGODB_URI environment variable to heroku, either through the terminal or from the ui.

To set the config var on Heroku execute the following: heroku config:set ENVNAME=valueOfEnv To view config vars that are set use: heroku config

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