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Here's the original TypeScript code I was using with Pulumi 1.x:
```const rawAzInfo = aws.getAvailabilityZones({
    state: "available",
});
let azNames: Array&lt;string&gt; = rawAzInfo.names;
let numberOfAZs: number = azNames.length;```

Here's what I was trying to use w/ Pulumi 2.x:
```const rawAzInfo = pulumi.output(aws.getAvailabilityZones({
    state: "available",
}));
let azNames = rawAzInfo.apply(rawAzInfo =&gt; rawAzInfo.names);
let numberOfAZs = azNames.length;```
TS complains that I can't define `azNames` as `Array&lt;string&gt;` because of type mismatch. If I remove the type definition, then I can't define `numberOfAZs` as a `number` due to type mismatch, and then that breaks some numerical operations later in the code.

As a relative newcomer to TypeScript, I'm a bit lost on how I can resolve this. Suggestions?

Since you’ll end up using the number later on, I would treat it as a promise (instead of wrapping in output). Then, either write your code w/in the `then` of the promise or use <https://www.pulumi.com/docs/intro/languages/javascript/#entrypoint> to use top-level `await`

Thanks. Can you suggest some reading that might help me better understand working with promises? I've tried a couple variations of using `then` to no avail, so I think I need to spend some time understanding the concepts a bit better.

I don’t have a “go to” resource for that. I’ve heard good things about <https://www.executeprogram.com/> — and their concurrency lesson seems to be among the free lessons you can try.