async-promise-queue/index.js

wrapper around async.queue to make some common usages simpler

'use strict';
var debug = require('debug')('async-promise-queue:');

// helper function that promisifies the queue
module.exports = function queue(worker, work, concurrency) {
  debug('started, with concurrency=' + concurrency)
  return new Promise(function(resolve, reject) {
    if (work.length === 0) {
      resolve();
    } else {
      var q = require('async').queue(worker, concurrency);
      var firstError;
      q.drain = resolve;
      q.error = function(error) {
        if (firstError === undefined) {
          // only reject with the first error;
          firstError = error;
        }

        // don't start any new work
        q.kill();

        // but wait until all pending work completes before reporting
        q.drain = function() {
          reject(firstError);
        };

      };
      q.push(work);
    }
  });
};

Object.defineProperty(module.exports, 'async', {
  get: function() {
    return require('async');
  }
});