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promise-sugar

2.0.1 • Public • Published

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(function(n){
    return n / 2
})
.then(function(n){
    return n * 3
})
.then(log) // -> 15
.catch(logError)

into this

sweeten(10)
(function(n){
    return n / 2
})
(function(n){
    return n * 3
})
(log, logError) // -> 15
(null, logError) // .catch

2 ) and this

// Given two existing promises A and B
A
.then(function () { return B; } ) // wait for A and B and return B's value
.then(log) // -> B's value

into this

A(B)
(log) // -> B's value

where

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

That's basically it!

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

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

Thunks is different from Promise-sugar an 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
  • Add promise-sugar.js to 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+

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

Here are some helper method of Promise-sugar:

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

Examples

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

let result = sweeten(fetch('/my/api'))
             (function(res) { return 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:

var myStuff = new sweeten(function (resolve, rejext){
    setTimeout(resolve, 100, Math.random());
});
 
myStuff(function(myNumber){/*...*/}, function(error){/*...*/});

Install

npm i promise-sugar

DownloadsWeekly Downloads

116

Version

2.0.1

License

MIT

Unpacked Size

38.3 kB

Total Files

9

Last publish

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