Lecture List

02 Callbacks vs Promises

03 Callbacks vs Thens

04 Course Map

• JavaScript Promises - Jake Archibald

05 Promise Timeline

06 Quiz: Async Scenarios

07 Syntax

Cam says: whoops, I don't actually have a good link for you at the moment. However, I can explain a little further. Try running this code in your browser.

new Promise(function(resolve) {
  console.log('first');
  resolve();
  console.log('second');
}).then(function() {
  console.log('third');
});

You'll notice that'first','second'and'third'all get logged. Most notably,'second'gets logged despite the fact that it comes afterresolve().

Around 2:11, I start talking about passing values orundefinedthroughresolve()andreject()to.thenand.catch. The values themselves aren't being passed to.thenor.catch, rather they're being passed to thefunctionscalled by.thenor.catch.

08 Quiz: Write Your First Promise

Instructions

1. Download setTimeout-start.zip from the Supporting Materials Section.
2. Wrap setTimeout in a Promise inside the wait() function. resolve() in setTimeout's callback.
3. console.log(this) inside the Promise and observe the results.
4. Make sure wait() returns the Promise too!

Check outsetTimeout-solution.zipin the Supporting Materials Section to see my code!

09 Quiz: Wrapping readyState

Instructions

1. Download readyState-start.zip in the downloadables section.
2. Set network throttling so that the page isn't ready instantly. (Also, it's generally a good practice to have some throttling when testing sites. It'll help you see your site's performance from your users' perspectives.)
3. Wrap an event listener for readystatechange in a Promise.
4. If document.readyState is not 'loading', resolve().
5. Test by chaining wrapperResolved(). If all goes well, you should see "Resolved" on the page!

More on document.readyState