mdaz78 / async-js-the-hard-parts

The Hard Parts of Asynchronous JS by Will Sentance

Promises Challenges

Challenge 1

Let's start by reviewing asynchronous functions! Using setTimeout, print the string 'Hello!' after 1000ms.

Challenge 2

Create a promise. Have it resolve with a value of 'Resolved!' in resolve after a delay of 1000ms, using setTimeout. Print the contents of the promise after it has been resolved by passing console.log to .then

Challenge 3

Create another promise. Now have it reject with a value of "Rejected!" without using setTimeout. Print the contents of the promise after it has been rejected by passing console.log to .catch

Challenge 4

Promises are asynchronous and we're now going to prove that they indeed are! Create a promise and have it resolve with the value of "Promise has been resolved!" Then uncomment the code at bottom of Challenge 4. What order do we expect "Promise has been resolved!" and "I'm not the promise!" to print? Why?

Challenge 5

Write a function delay that returns a promise. And that promise should return a setTimeout that calls resolve after 1000ms

Challenge 6

This challenge we'll chain promises together using ".then" Create two variables: firstPromise and secondPromise Set secondPromise to be a promise that resolves to "Second!" Set firstPromise to be a promise that resolves to secondPromise Call the firstPromise with a ".then", which will return the secondPromise promise. Then print the contents of the promise after it has been resolved by passing console.log to .then

Challenge 7

We have a API that gets data from a database, it takes an index parameter and returns a promise Your challenge is to use Promise.all to make 3 API calls and return all the data when the calls are complete

Iterators Challenges

Challenge 1

1. Create a for loop that iterates through an array and returns the sum of the elements of the array.
2. Create a functional iterator for an array that returns each value of the array when called, one element at a time.

Challenge 2

Create an iterator with a next method that returns each value of the array when .next is called.

Challenge 3

Write code to iterate through an entire array using your nextIterator and sum the values.

Challenge 4

Create an iterator with a next method that returns each value of a set when .next is called

Challenge 5

Create an iterator with a next method that returns an array with two elements (where the first element is the index and the second is the value at that index) when .next is called.

Challenge 6

Create an iterator that returns each word from a string of words on the call of its `.next method (hint: use regex!) Then attach it as a method to the prototype of a constructor Words. Hint: research Symbol.iterator!

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Solution => Link to the solution for the Exercises