Promise.all is similar to Promise.resolve; the arguments are resolved as promises. The difference is that instead of a single result, Promise.all accepts an iterable argument, each member of which is resolved individually.

In the preceding example, you can see that each of the promises is initiated immediately. Two of them are able to complete while performGuidanceDiagnostic continues. The promise returned by Promise.all is fulfilled when all the constituent promises have been resolved.

The results of the promises are combined into an array and propagated down the chain. You can see that three references to rocket are packed into the results argument. And you can see that the operations of each promise have been performed on the resulting object.