jerryzlau/twitter-mobile-app

Twitter clone on GraphQL, Apollo and ReactNative

Twitter Clone

Notes:

• node doesn't understand ES6 syntax, however, babel can handle that problem, the line below installs babel and solve the problem:

  npm install babel-cli babel-plugin-transform-object-rest-spread babel-preset-env --save
  

• add run server line to package.json scripts: this also adds nodemon to recompile server on change

  "dev": "cross-env NODE_ENV=dev nodemon --exec babel-node src/index.js"
  

  run server by:

  npm run-script dev
  

• A very strict but good linter

  npm install eslint eslint-config-equimper prettier eslint-config-prettier --save
  

  then

  add file .eslintrc

    {
      "extends": [
        "equimper",
        "prettier"
      ]
    }
  

• GraphQL Query fetch usage on console

  • get all tweets

    {
      getTweets{
        _id
        text
      }
    }
  

  • get target tweet

    <!-- pass in an id to fetch and specify what fields is wanted as response -->
    {
      getTweet(_id: "id") {
        _id
        text
      }
    }
  

• GraphQL Schema date type

1. Install graphql date:

   npm install graphql-date --save
   

2. In schema add to the top:

   scalar Date
   

   Then we can specify a Date type:

   type {
     createdAt: Date!
   }
   

3. In the resolvers index specify a Date along with Query and Mutation

Questions I asked along the way

• What is express?

  Express organizes application into an MVC architecture

• What is mongoose?

  Mongoose is the ORM, it is used for modeling mongodb

• PostgreSQL vs MongoDB?

  • PostgreSQL:

    • Vertical Scaling(doesn't scale very well)
    • Could scale horizontally but need third party solution
    • ACID database

  • MongoDB:

    • Horizontal Scaling (good stuff, better for scaling)
    • Automatic database sharding
    • Potential loss of data

• Horizontal Scaling vs Vertical Scaling?

  • Horizontal Scaling:
    • Scale by adding more machines
    • Easier to scale dynamically
  • Vertical Scaling:
    • Scale by adding more CPU, it is
    • Limited to the capacity of a single machine

• What is async await?

  • async/await is similar to promise/then
  • async can take in a call back and within that callback tell a variable to wait for result from another function call inside that callback
  • promise itself is the result of a function

• How does Array.from create array with size n?

  Array.from({length: 2}) = [undefined, undefined];
  Array.from({length: 2}, (a, b) => b) = [0,1];
  Array.from([1,2,3], x => x + x) = [2,4,6];