Promises and Fetch

Question 1

Can you pause execution of code in JavaScript?

Answer 1

No, there is no idea. You can’t sleep the thread

Question 2

What do promises try to solve?

Answer 2

The situation where you are waiting for data to come back from the internet or another source

Question 3

What are the three states of promises?

Answer 3

Unresolved, resolved, rejected

1) Unresolved - waiting for something to finish
2) Resolved - something finished and it’s all okay
3) Rejected - something finished and something went bad

Question 4

After the unresolved status, what happens when you enter resolved or rejected?

Answer 4

Then or Catch (Respectfully)

You also utilize the then or catch with callbacks

Question 5

When do you use promises?

Answer 5

When you do AJAX requests. However, you can make an AJAX request without a promise and a promise without an AJAX request

Question 6

Explain how catch operates

Answer 6

When a promise hits the resolved state and the callback function is ran, you can then call ‘variable name’.then() with a callback inside to run some additional code.

promise = new Promise((resolve, reject) =>{

reject();

});

promise

.then(() => console.log(“Finally Finished!”))

.then(()=> console.log(“I was also ran!”))

.catch(()=> console.log(‘Uh on!’))

Question 7

What is the most popular handler to use with promises?

Answer 7

The Fetch handler is the most popular in ES6

Question 8

What are the shortcomings of fetch?

Answer 8

You need to call .json() for your first then, then you can call data to get the data that you need

BIG: If you are using fetch and it has .then and . catch. IF the server returms back an error, it does NOT enter the .catch statement which is different from EVERY library. Only enters if the request flat out fails.