function getDiffieHellman
Usage in Deno
```typescript import { getDiffieHellman } from "node:node__crypto.d.ts"; ```
getDiffieHellman(groupName: string): DiffieHellmanGroup
Creates a predefined `DiffieHellmanGroup` key exchange object. The
supported groups are listed in the documentation for `DiffieHellmanGroup`.
The returned object mimics the interface of objects created by [createDiffieHellman](../.././node__crypto.d.ts/~/createDiffieHellman), but will not allow changing
the keys (with `diffieHellman.setPublicKey()`, for example). The
advantage of using this method is that the parties do not have to
generate nor exchange a group modulus beforehand, saving both processor
and communication time.
Example (obtaining a shared secret):
```js
const {
getDiffieHellman,
} = await import('node:crypto');
const alice = getDiffieHellman('modp14');
const bob = getDiffieHellman('modp14');
alice.generateKeys();
bob.generateKeys();
const aliceSecret = alice.computeSecret(bob.getPublicKey(), null, 'hex');
const bobSecret = bob.computeSecret(alice.getPublicKey(), null, 'hex');
// aliceSecret and bobSecret should be the same
console.log(aliceSecret === bobSecret);
```