JavaScript Promises

Objective

Your objective is to turn the given function into a new promise, and handle success or failures from the asynchronous code.

Getting Started

Repo link: JavaScript Promises

1. Open your command line and navigate to your repos directory (if you do not have a repos folder, then you can use mkdir repos to create one)
2. Use this template repository to start a new project in your repos folder: git clone <repo_name>
3. cd repo_name to navigate into your new repo directory
4. Start Visual Studio Code and select 'Open Folder'. Then select repo_name to open the folder in the editor (or just type code . in your terminal inside the repo directory)
5. Follow the instructions on the README.md file to complete exercises
6. Open the app.js file to get started

Exercise 1

You will start with the following code in your app.js file:

function watchTutorialCallback(callback, errorCallback) {
  let userLeft = false;

  if (userLeft) {
    errorCallback("User left.");
  } else {
    callback("Thumbs up and Subscribe!");
  }
}

watchTutorialCallback(
  (message) => {
    console.log(message);
  },
  (error) => {
    console.log(error.name + " " + error.message);
  }
);

The above function can be replicated as a Promise.

1. Declare a variable watching and assign it a new promise object
2. Inside of the promise constructor, declare a variable named userLeft.
3. Add a if/else conditional that checks if userLeft is true
4. If userLeft is true, call the reject method with "User left."
5. If false, call the resolve method with "Thumbs up and subscribe!"

Exercise 2

Once you have created your new promise:

1. Call watching and add a promise chain using .then and .catch
2. Pass in a function callback to .then that takes in a message and console.log's the message
3. Pass in a function callback to .catch that takes in an error and console.log's the error

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Exercise Walkthrough Documentation