Promise.all方法

function asyncRandom() {
  return new Promise(function(resolve, reject) {
    setTimeout(resolve, 100, Math.floor(Math.random() * 100) + 1);
  });
}

let numbers = [];
function genNumber(count = 100) {
  const promises = [];
  const handleNumber = n => numbers.push(n);
  for (let i = 0; i < count; i++) {
    promises.push(asyncRandom().then(handleNumber));
  }
  return promises;
}


Promise.all(genNumber(20)).then(() => {
      console.log(numbers);
    });