method Http2ServerResponse.prototype.getHeaderNames
Usage in Deno
```typescript import { Http2ServerResponse } from "node:node__http2.d.ts"; ```
Http2ServerResponse.prototype.getHeaderNames(): string[]
Returns an array containing the unique names of the current outgoing headers.
All header names are lowercase.
```js
response.setHeader('Foo', 'bar');
response.setHeader('Set-Cookie', ['foo=bar', 'bar=baz']);
const headerNames = response.getHeaderNames();
// headerNames === ['foo', 'set-cookie']
```
string[]