Instructor Notes

  • Class components section
    • Students often get tripped on converting between functional & class components
    • Common problem - render(props) instead of using this.props
  • Uses the state = {} class property pattern
    • This avoids having to use a constructor and calling super(props)
      • Students won't have encountered class inheritance, so this can cause confusion
  • Uses the foo = () => {} method style
    • For non-React-provided methods (e.g. lifecycle methods)
    • Avoids issues with this. Which is a huge pain to explain/understand, so we avoid it
    • This syntax isn't part of the spec yet, but CRA has babel plugin for it
    • Ensure that you cover the exception (lifecycle methods)
  • Unmounting
    • Open dev tools and show how DOM updates - shows that the DOM is changing in response to React
  • Lifecycle
    • The lifecycle diagram has been edited to simplify to just the lifecycle methods that we're interested in
  • Clock exercise
    • Make sure they copy/paste the example code - post in Slack
    • Demonstrates the need to tear down subscriptions set up
    • Might need to touch on memory leaks
      • this is hard for them to grasp as "just a console.log" seems like it wouldn't take much memory
  • Data fetching
    • Touch on .then(res => res.json()) - turns response into JSON
    • API is from Nasa - fetches Curiosity rover image from the given date
    • Error handling code to get fetch to throw an error on a non-200 response:
.then((res) => {
if (res.ok) {
return res
} else {
throw new Error('HTTP error')
}
})