Exploring the Flatmap Promise Feature in JavaScript

Question

Exploring the Flatmap Promise Feature in JavaScript

I'm sure this question has been asked before, but is there a way to flatten a promise in JavaScript?

For example:

let justAPromise: Promise<something> = aPromise.flatMap( a => getAnotherPromise());

Or like this:

let promiseOfPromise: Promise<Promise<something>> = aPromise.then( a => getAnotherPromise());
let justAPromise: Promise<something> = promiseOfPromise.flatten();

UPDATE:

To clarify the concept of flattening a promise. I distinguish between these two scenarios. The first is a promise of an integer, and the second is a promise of a promise of an integer:

Promise.resolve(23);

Promise.resolve("whatever").then(a => Promise.resolve(23));

javascript typescript es6-promise

Answer 1

Answer №1

To effectively chain promises together, simply follow this pattern:

let chainedPromise: Promise<result> = initialPromise.then( someData => getAnotherPromise());

The snippet below demonstrates how the chaining works in action:

var initialPromise = new Promise(resolve => setTimeout(() => resolve("first"), 1000));
var getAnotherPromise = () => new Promise(resolve => setTimeout(() => resolve("second"), 1000));
var chainedPromise = initialPromise.then(someData => getAnotherPromise());
chainedPromise.then(result => console.log(result)); // <-- this will output "second"

Answer 2

To effectively chain promises together, simply follow this pattern:

let chainedPromise: Promise<result> = initialPromise.then( someData => getAnotherPromise());

The snippet below demonstrates how the chaining works in action:

var initialPromise = new Promise(resolve => setTimeout(() => resolve("first"), 1000));
var getAnotherPromise = () => new Promise(resolve => setTimeout(() => resolve("second"), 1000));
var chainedPromise = initialPromise.then(someData => getAnotherPromise());
chainedPromise.then(result => console.log(result)); // <-- this will output "second"

Exploring the Flatmap Promise Feature in JavaScript

Answer №1

Similar questions

changing the contents of an array within the current state

Tips for establishing a universal onkeydown listener for all frames within a webpage?

Is there a way to set columns as initially hidden in MaterialTable?

Tips for saving an Angular project for offline use

Tips for positioning a sticky div underneath a stationary header

What's the best way to ensure that only the most recent 100 entries are retained in a CSV file

The PHP function is returning an undefined value in JavaScript

Iterate through a intricate array of JavaScript objects to extract their values

The toggle for hiding and showing, along with changing the button color, is not functioning properly due to

Choosing a nested object within a JavaScript object

Is it possible to display an unordered list upon clicking a button without relying on CSS and still achieve identical visual outcomes?

How can I retrieve user input from a text box and showcase it in an array format using jQuery?

What is the best way to adjust a map to completely fill the screen?

Using the original type's keys to index a mapped type

Empty the localStorage when terminating the IE process using the Task Manager

Is it possible to detect a swipe event without relying on third-party libraries

Struggling to construct a binary tree as my descendants are not arranged in the right sequence

Exploring Angular 12: utilizing rxjs observables with chained subscriptions for enhanced functionality and robust error handling

Guide to implementing a dropdown menu for selecting countries in Angular

Setting up JW Player with a YouTube Embed URL