closure - 2种实现

poll.js

function getStatus() {
  const random = Math.random() * 10
  if (random > 5) {
    return true
  } else {
    return false
  }
}

function callback() {
  console.log('执行完毕')
}

function poll(getStatus, callback) {
  let time = 1000
  return function del() {
    if (getStatus()) {
      console.log('getStatus执行了')
      setTimeout(() => {
        del()
      }, time)
      time *= 1.5
    } else {
      callback()
    }
  }
}

poll(getStatus, callback)();

poll2.js

const callback = () => console.log('done');
const getStatus = () => !!Math.round(Math.random());
const delay = ms => new Promise(resolve => setTimeout(resolve, ms));

function polling(getStatus, callback) {
  let delta = 1000;
  let start;

  return async function idle() {
    if (getStatus()) {
      console.log('idle');
      await delay(delta);
      delta *= 1.5;
      return idle();
    }

    return callback();
  };
}

polling(getStatus, callback)()