Promises Lesson

Agenda

Synchronous vs Asynchronous
Turn and Talk: What are some situations where synchronous and asynchronous schemes occurr?
- Think of programming and non programming examples
Aside: The JS event loop
- Draw this on the board with help from students
Stuff that is async
- DOM events
- setTimeout
- setInterval
- Promises
- Fetch/XHR
- setState
How you know async stuff to work now: Callbacks
- Call for real life examples of callbacks (starbucks)
What's the problem with callbacks?
- Call for suggestions here
Promises: They solve the problems with callbacks
- Three States
  - Pending
  - Resolved
  - Rejected
- The promise lifecycle
- Chaining Promises
- Promise methods - group up then present
  - Promise.all()
  - Promise.prototype.catch()
  - Promise.prototype.then()
  - Promise.race()
  - Promise.reject()
  - Promise.resolve()
window.fetch example
- Use window.fetch to grab some data