How to wait for another JS to load to proceed operation?

Question

I have an issue. One of my JS scripts needs Facebook SDK and Twitter widgets JS to load first. Facebook creates FB object, Twitter creates twttr ob

Answer 1

const checkIfLoaded = ('lib', cb) => {
  const interval = setInterval(() => {
    if (lib) {
      typeof cb === 'function' && cb();
      clearInterval(interval);
    } else {
      console.log('not yet');
    }
  }, 100);
}