promise-dot-all

Recreate Promise.all

Recreate the native Promise.all JavaScript function.

Background

Promises are a cornerstone of writing asynchronous JavaScript. Similar to callbacks, they allow us to easily defer slow code for execution at a later time so as to not block other code on the stack. Unlike callbacks, promises are able to be chained together, making them more readable and less nested than successive callbacks.

Promise.all is used when you want to wait for a collection of promises to all resolve before doing anything with their return values. In its simplest form, Promise.all takes in an array of promises and returns a single promise. The returned promise resolves when all of the promises in the array argument have resolved.

Using Promise.all

const p1 = Promise.resolve('first')
const p2 = Promise.resolve('second')

Promise.all([p1, p2]).then(values =>
  console.log(values) // ['first', 'second']
)

Getting Started

The file you will be editing is promise-dot-all.js.

The promise-dot-all-test.js file includes a test suite to run your code against.

Run node promise-dot-all-test.js to run the test suite in full. As you write code to pass tests, make sure you unskip succeeding tests by changing test.skip to just test.