Wait for promise in a forEach loop

Question

I am receiving a list of books from a database as a Promise.

If the initial list of books is successfully loaded, the books are further processed by passing them to

Answer 1

Modify the addInfo method so it stores the promises in an array, and return Promise.all instead, which will resolve when all the promises have resolved.

Assuming your methods returns a promise, and it looks like they do, something like

addInfo: function(books) {
  let promises = books.map(function(book) {
    return client.itemLookup({
      idType        : 'ISBN',
      itemId        : book.isbn,
      responseGroup : 'ItemAttributes,Images'
    }).then(function(results) {
      return {
        // The additional info from result gets added here
      }
    });
  })
  return Promise.all(promises); // catch errors where you call "addInfo"
}