x.js

new Promise((resolve, reject) => {
  const timeout = setTimeout(() => {
    clearInterval(interval);
    reject(new Error('timed out'));
  }, 5000);
  const interval = setInterval(() => {
    const x = doSomething();
    if (x !== undefined) {
      clearInterval(interval);
      clearTimeout(timeout);
      resolve(x);
    }
  }, 1000);
}).then((x) => {
  console.log('x is', x);
});