JS/Front-end

• Warning: React.createElement: type is invalid -- expected a string (for built-in components) or a class/function (for composite components) but got: undefined. You likely forgot to export your component from the file it's defined in, or you might have mixed up default and named imports. => Got this from importing Tabs and Tab from react, not react-bootstrap.
• JS can’t sort if there’s a null. You need to make them ‘’ if ever.
• Destructuring a two level hash

class Listing extends Component {
  render() {
    const {
      listing: {
        location: {
          city,
          state,
          country
        }
      }
    } = this.props;

return (
      <p>Location: {city}, {state}, {country}</p>
    )
  }
}

• Stateless functional components: should not have functions inside lol. Bind them from outside. Reference
• Prefetching, preloading, prebrowsing
  • Pre-fetching: A way to hint to the browser about resources that are going to or might be used in the future.
  • DNS pre-fetching: Notifies the client that there are assets we’ll need later from a specific URL so the browser can resolve the DNS as quickly as possible. <link rel="dns-prefetch" href="//example.com">

Ruby

• map then tap is ugly but it works lol.

Cryptocurrency

• ASIC: Application-specific integrated circuit, an IC customized for a particular use (voice recording, Bitcoin mining).