function makeWorker() {
  return new Worker(URL.createObjectURL(new Blob([
`onmessage = function(message) {
  const data = message.data;
  postMessage({ status: 1 });
  postMessage({ result: eval.call(this, data.code), status: 2 });
}`], { type: 'text/javascript' })));
}

function timedEval(code, timeout = 1000) {
  return new Promise((resolve, reject) => {
    const worker = makeWorker();

    worker.onmessage = function(message) {
      const data = message.data;
      if (data.status === 1) {
        setTimeout(() => {
          worker.terminate();
          reject(new Error('Script evaluation took too long!'));
        }, timeout);
      } else if (data.status === 2) {
        resolve(data.result);
      }
    };

    worker.postMessage({ code, status: 0 });
  });
}