promise-reflect

promise-reflect

Description

A simple function that forces a promise to resolve, returning an object that indicates the actual promise status and the underlying object returned from the original promise.

//If underlying promise resolves
{
  "data": {
     //Object returned by underlying promise
  },
  "status":"resolved"
}

//If underlying promise rejects
{
  "error": {
     //Object returned by underlying promise
  },
  "status":"rejected"
}

Inspiration

The reason for this functionallity to to augment Promise.all(...) to allow for some promises to reject without losing the data returned from those that succeeded.

See the following StackOverflow post: http://stackoverflow.com/questions/31424561/wait-until-all-es6-promises-complete-even-rejected-promises

Example Usage

'use strict'

let promiseReflect = require('../promise-reflect');

let p1 = new Promise((resolve, reject) => {
  setTimeout(resolve, 1000, "one");
});
let p2 = new Promise((resolve, reject) => {
  setTimeout(resolve, 2000, "two");
});
let p3 = new Promise((resolve, reject) => {
  setTimeout(resolve, 3000, "three");
});
let p4 = new Promise((resolve, reject) => {
  setTimeout(resolve, 4000, "four");
});
let p5 = new Promise((resolve, reject) => {
  reject("reject-one");
});
let p6 = new Promise((resolve, reject) => {
  reject("reject-two");
});

let promisesArray = [p1, p2, p3, p4, p5, p6]

Promise.all(promisesArray.map(promiseReflect))
    .then(values => {
      let resolved = values.filter(value => value.status === 'resolved');
      let rejected = values.filter(value => value.status === 'rejected');
      console.log(`Values: ${JSON.stringify(values)}`);
      console.log(`Resolved: ${JSON.stringify(resolved)}`);
      console.log(`Rejected: ${JSON.stringify(rejected)}`);
    })
    .catch(reason => {
      console.log(`Shouldn't get here as all promises resolve when put through promise-reflect`);
    });
    
// Output
// Values: [{"data":"one","status":"resolved"},{"data":"two","status":"resolved"},{"data":"three","status":"resolved"},{"data":"four","status":"resolved"},{"error":"reject-one","status":"rejected"},{"error":"reject-two","status":"rejected"}]
// Resolved: [{"data":"one","status":"resolved"},{"data":"two","status":"resolved"},{"data":"three","status":"resolved"},{"data":"four","status":"resolved"}]
// Rejected: [{"error":"reject-one","status":"rejected"},{"error":"reject-two","status":"rejected"}]

##Credit The logic in this package is heavily based upon the question response by Benjamin Gruenbaum seen here: http://stackoverflow.com/a/31424853/3164844