Function append

packages/core/src/utils/envelope.ts:97–103

(next: string | Uint8Array)

  let parts: string | Uint8Array[] = JSON.stringify(envHeaders);

  function append(next: string | Uint8Array): void {
    if (typeof parts === 'string') {
      parts = typeof next === 'string' ? parts + next : [encodeUTF8(parts), next];
    } else {
      parts.push(typeof next === 'string' ? encodeUTF8(next) : next);
    }
  }

  for (const item of items) {
    const [itemHeaders, payload] = item;