Promises in sequence.

sequence.js

// Syncronus running of promises to process an array of objs (or anything really) in a series.
// given an array:

var items = [{type: 'peanuts', type: 'carrots'}];

// we instantly "resolve" a promise for force exceucution
let sequence = Promise.resolve();

for (let item of items) {
  sequence = sequence.then(() => {
    return new Promise((resolve, reject) => {
      db.insertOrUpdateThing(item, {err, dbItem} => {
         // yay we have a new item in our db
         if (err) {
          return reject(err);
         }
         return resolve(dbItem);
      });
    })
  });
}

return sequence;
// or
sequence
  .then(items => {
    // array of values returned from resolve fxns
    // do things
  })
  .catch(err => {
    console.log(err);
  })