QueryIterator should be a proper iterator

[spencerhakim]

ES2015 provides a standard for implementing iterators in JavaScript, and it's rather misleading that something called QueryIterator doesn't actually support this.

[jcormont]

A true ES2015 iterator would be impossible to implement, because data is fetched asynchronously (in chunks). The iterator has to return something synchronously from the next() call though, and so it would never be able to set .done until the data is loaded (not synchronously, i.e. not right away so a synchronous for loop would either quit early or loop forever).

However, there is in fact also an upcoming spec for async iterators, where the next() call returns a Promise for the done/value object. At the moment this hasn't really been implemented yet in Node though (we need Symbol.asyncIterator for this to work fully).

The good news is that the next version of TypeScript (2.3) will include a shim for this. See this issue. Once that lands I'll add it to my project documentdb-typescript, and you'll be able to write a loop in TypeScript as if everything was synchronous for await (const myResult of coll.queryDocuments(...)) { ... }.

[christopheranderson]

I like this idea for query.forEach() in the v2 SDK. I was thinking the same thing before seeing this issue.

[southpolesteve]

We have recently announced deprecation version 1.x of the Azure Cosmos JavaScript SDK. We will end support for the documentdb package and this repo on August 30, 2020. Please update to our new package @azure/cosmos as soon as possible. If you encounter any issues, you can raise them in the Azure central JS SDK repo. If something is preventing you from upgrading to the latest version of the SDK, you can always email me directly: stfaul@microsoft.com