metal-promise

/*!
 * Promises polyfill from Google's Closure Library in ES6.
 *
 *      Copyright 2013 The Closure Library Authors. All Rights Reserved.
 *
 * Promise support is not ready on all supported browsers,
 * therefore core.js is temporarily using Google's promises as polyfill. It
 * supports cancellable promises and has clean and fast implementation.
 */

Use

Simple use case

import CancellablePromise from 'metal-promise';

new CancellablePromise(function(resolve, reject) {
  asyncFunction(function(err) {
    if (err) {
      reject(err);
    }
    else {
      resolve();
    }
  });
})
.then(function() {
  // Invoked once resolved
})
.catch(function(err) {
  // Invoked once rejected
});

Progress tracking

In addition to Google Closure's implementation of Promise, the ProgressPromise class is also provided for tracking the progress of an async process.

import {ProgressPromise} from 'metal-promise';

new ProgressPromise(function(resolve, reject, progress) {
  progress(0.3);
  progress(0.5);
  progress(0.7);
  progress(0.9);

  setTimeout(function() {
    resolve();
  }, 100);
})
.progress(progress => {
  // Will invoke 4 times, 0.3, 0.5, 0.7, 0.9
})
.then(function() {
  // Invoked after all progress calls
});

Note that the progress function must be invoked with a number between 0 and 1.

progress(2); // TypeError: The progress percentage should be a number between 0 and 1

It also cannot be invoked with a smaller number than the previous call.

progress(0.3);
progress(0.1); // Error: The progress percentage can't be lower than the previous percentage

Advanced use cases

To see more advanced documentation, please visit Google Closure Library's documentation;

Setup

1. Install a recent release of NodeJS if you don't have it yet.

2. Install local dependencies:

npm install

3. Run the tests:

npm test

Contributing

Check out the contributing guidelines for more information.