Promise-based operations in sequence, with Bluebird

array_promises_in_sequence.js

var Promise = require('bluebird'),
    data = ['a', 'b', 'c', 'd', null, 'e'];
 
/**
 * A long running task to run for each element of the array.
 * It must return a promise
 */
function doThing(arg) {
  return new Promise(
    function (resolve, reject) {
 
      setTimeout(function () {
        console.log(arg);
        if (arg) {
          resolve('resolved - ' + arg);
        } else {
          reject('Error: falsy value');
        }
      }, 1000);
    }
  );
}
 
console.log('and we\'re off!');
Promise.each(data, doThing);