es6-promise-extended v1.1.1

es6-promise-extended

A lightweight extension to the es6-promise library, which brings a finally clause and deferred promises, alongside the es6-promise Promise object and static methods.

Building and testing

• npm install To install all dependencies
• npm test To run the tests
• npm run watch-tests To run the tests and watch the code for changes
• npm run lint To lint the code

Usage

To install:

npm install es6-promise-extended

To use:

var ExtendedPromise = require('es6-promise-extended');

Promise

Promises are created as shown:

var promise = new ExtendedPromise.Promise(function (resolve, reject) {
	resolve('someValue');
	// OR
	reject('someError');
});

finally

Finally is always called after the rejection or fulfillment of a promise, as shown:

var promise = new ExtendedPromise.Promise(function (resolve, reject) {
	resolve(10);
});

promise
	.then(function (result) {
		return result * 2;
	})
	.finally(function (result) {
		console.log('Finally!', result);
	});

// Finally! 20

var promise = new ExtendedPromise.Promise(function (resolve, reject) {
	reject();
});

promise
	.catch(function (result) {
		return 'Error!';
	})
	.finally(function (result) {
		console.log('Finally!', result);
	});

// Finally! Error!

defer

defer allows you to pass the control of the promise onto a consumer, who can control when to resolve or reject the promise, as shown:

Resolve

var deferred = ExtendedPromise.defer();

deferred.promise
	.then(function (msg) {
		console.log('Resolved!', msg);
	});

deferred.resolve('yo!');

// Resolved! yo!

Reject

var deferred = ExtendedPromise.defer();

deferred.promise
	.catch(function (msg) {
		console.log('Rejected!', msg);
	});

deferred.reject('Something went wrong..');

// Rejected! Something went wrong..

Finally

It is compatible with the finally method too:

var deferred = ExtendedPromise.defer();

deferred.promise
	.finally(function (msg) {
		console.log('Finally!', msg);
	});

deferred.resolve('I always run.');

// Finally! I always run.

Promise.all

all resolves when all the promises passed to it have resolved or rejected

var promise1 = new ExtendedPromise.Promise(function (resolve, reject) {
	setTimeout(function () {
		resolve(10);
	}, 1);
});
var promise2 = new ExtendedPromise.Promise(function (resolve, reject) {
	setTimeout(function () {
		resolve(20);
	}, 2);
});

ExtendedPromise.all([ promise1, promise2 ].then(function (result) {
	console.log('Resolved!', result[0], result[1]);
});

// Resolved! 10 20

Promise.race

race resolves as soon as a promise passed to it has been resolved or rejected

var promise1 = new ExtendedPromise.Promise(function (resolve, reject) {
	setTimeout(function () {
		resolve(10);
	}, 1);
});
var promise2 = new ExtendedPromise.Promise(function (resolve, reject) {
	setTimeout(function () {
		resolve(20);
	}, 2);
});

ExtendedPromise.race([ promise1, promise2 ]).then(function (result) {
	console.log('Resolved!', result);
});

// Resolved! 10

Promise.resolve

Returns a promise that is resolved

var promise = ExtendedPromise.resolve(10);

promise.then(function (result) {
	console.log('Resolved!', result);
});

// Resolved! 10

Promise.reject

Returns a promise that is rejected

var promise = ExtendedPromise.reject('I have been rejected!');

promise.catch(function (msg) {
	console.log('Error!', msg);
});

// Resolved! I have been rejected!