Fibonacci runtime function

Use a runtime function when the caller should await a result from another JS runtime. This is the smallest possible example.

import { call, runtimeFunction } from '@react-native-runtimes/core';

function fibonacciNumber(n: number): number {
  if (n < 2) {
    return n;
  }

  return fibonacciNumber(n - 1) + fibonacciNumber(n - 2);
}

export const fibonacci = runtimeFunction((n: number) => {
  return {
    input: n,
    result: fibonacciNumber(n),
    computedAt: new Date().toISOString(),
  };
});

const result = await call(fibonacci).on('fibonacci-worker-runtime')(38);

The sample app includes this as the Fibonacci screen.

What to look at

• The worker runtime is named fibonacci-worker-runtime — that name is the contract between caller and callee. Both reference the same string.
• The function is exported and wrapped in runtimeFunction(...). Without those two, Metro can't register it.
• Arguments and the return value are JSON-safe.

Variations

Want the function to always live on the worker runtime? Use the directive shortcut so the call site stays ordinary:

async function fibonacci(n: number) {
  'fibonacci-worker-runtime';
  return fibonacciNumber(n);
}

const result = await fibonacci(38);

See Scheduling functions on another runtime for the full API.