zcaceres

Sequelize: Step-By-Step

Sequelize is a powerful library in Javascript that makes it easy to manage a SQL database. Sequelize can layer over different protocols, but here we'll use PostgreSQL. At its core, Sequelize is an Object-Relational Mapper – meaning that it maps an object syntax onto our database schemas. Sequelize uses Node.JS and Javascript's object syntax to accomplish its mapping.

Under the hood, Sequelize used with PostgreSQL is several layers removed from our actual database:

1. First, we write our Sequelize, using Javascript objects to mimic the structure of our database tables.
2. Sequelize creates a SQL string and passes it to a lower-level library called pg (PostgreSQL).
3. pg connects to your PostgreSQL database and queries it or transforms its data.
4. pg passes the data back to Sequelize, which parses and returns that data as a Javascript object.

gaearon

// connect() is a function that injects Redux-related props into your component.
// You can inject data and callbacks that change that data by dispatching actions.
function connect(mapStateToProps, mapDispatchToProps) {
  // It lets us inject component as the last step so people can use it as a decorator.
  // Generally you don't need to worry about it.
  return function (WrappedComponent) {
    // It returns a component
    return class extends React.Component {
      render() {
        return (

vasanthk

System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

Basic Steps

1. Clarify and agree on the scope of the system

• User cases (description of sequences of events that, taken together, lead to a system doing something useful)
  • Who is going to use it?
  • How are they going to use it?