Showing posts from February, 2019

Using an async iterator on Node.js + S3

There isn't support for async iterators (for await...of) in Node.js v8.9 which is AWS Lambda's runtime. It's shame, as it’s a great feature that allows you to iterate over an iterable that returns as result asynchronously, i.e. retrieving another page from a database, using a compact for loop that feels synchronous but under the covers is actually done asynchronously.
Which means, if you want to use a library that written specifically to use it (e.g. Amazon DynamoDB QueryPaginator), you have to use an even more verbose syntax. However with a bit of re-purposing you can use a generator function that returns a Promise and if you await each promise given in the loop it will behave like an async iterator.