Promise syntactic sugar

No need to write .then in your promise chains. The promise is the .then function itself!

What it does

1 ) It allows you to convert this

Promise.resolve(10)
.then((n) => n / 2)
.then((n) => n * 3)
.then(log) // -> 15
.catch(logError)

into this

sweeten(10)
((n) => n / 2)
((n) => n * 3)
(log) // -> 15
(null, logError) // or .catch(logError)

2 ) and this

// Given two existing promises A and B
// wait for A and B and return B's value
log(await A.then(() => B)) // -> B's value

into this

log(await A(B)) // -> B's value

where

const log      = console.log.bind(console);
const logError = console.error.bind(console);

That's almost it! For More sugar see below.

A sweeten promise is still a thenable. Thus you can still await for it, or you could swap the Promise with the sweeten version in your old code and it should still work the same.

Promise-sugar tries to preserve all other behaviors of the Promise library used.

There is another library that implements a similar paradigm - thunks.

Thunks is different from Promise-sugar and more complex (a thunk is not a promise and it has no .catch() method).

You can play with it on jsBin

Install

• Copy promise-sugar.js to your project or install it using npm:

npm install promise-sugar --save

• Import promise-sugar.js into your app using import (ESM), require (AMD or CommonJs) or as a script tag.

import sweeten from 'promise-sugar';

const sweeten = require('promise-sugar');

<script src="https://unpkg.com/promise-sugar"></script>

• Make sure there is a Promise implementation or get a polyfill like es6-promise.

sweeten.usePromise(require('es6-promise').Promise); // polyfill

More sugar

Regardless of the Promise implementation used, all sweeten promises have the following methods:

sweeten(promise)
    .catch(onReject)   // Promite/A+
    .finally(callback) // not a Promise/A+ method
    .timeout(1000)     // reject in 1 sec, not a Promise/A+ method

If Promise.prototype.progress is defined, Promise-sugar will preserve it.

Here are some helper methods of Promise-sugar:

sweeten.when(value_or_thenable); // creates a sweeten promise
let deferred = sweeten.defer();  // creates a deferred with a sweeten .promise

sweeten.allValues(obj);          // Similar to Promise.all(list), but accepts an object with thenable values

if(sweeten.isThenable(any)) any.then(doStuff);

let waiter = sweeten.wait(123);  // setTimeout()
waiter.then(doStuffLater);
waiter.stop();                   // don't doStuffLater() (like clearTimeout())


function sum(a,b) { return a + b; }
let ssum = sweeten.fn(sum); // sweeten version of sum()
ssum(2, Promise.resolve(3))(log); // -> 5


// Promise/A+ sweet equivalents
sweeten.resolve(val)
sweeten.reject(val)
sweeten.race(list)
sweeten.all(list)
sweeten.any(list)
sweeten.allSettled(list)

Examples

Sweeten promises are just promises and functions (thens) at the same time:

let result = sweeten(fetch('/my/api'))
             ((res) => res.json())
;

// Now you have a simple function that contains your result
result(log);

// and it is still a promise!
result.catch(logError);

// and can be used as such
Promise.all([result, fetch('my/api/something/else')])
.then(/*...*/);

// or equivalent of the above
sweeten.all([result, fetch('my/api/something/else')])
(/*...*/);

Sweeten promise constructor:

let myStuff = new sweeten(function (resolve, rejext){
    setTimeout(resolve, 100, Math.random());
});

myStuff((myNumber) => {/*...*/}, (error) => {/*...*/});