/**
 * EXAMPLE1: 在 Promise 的 callback 中回傳另一個 Promise
 **/

const returnPromise = new Promise((resolve, reject) => {
  // 立即執行
  console.log('In first Promise, start callback')
  setTimeout(() => {
    let data = 10
    resolve(data)
    console.log('In fist Promise, resovle data')
  }, 1500)
})
// 在 Promise 的 Callback 中回傳另一個 Promise
.then((value) => {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      resolve(value + 3)
      console.log('In second Promise, resovle data')
    }, 1500)
  })
})
.then((value) => {
  console.log('In third then, the value is ' + value)
})
.catch((reason) => {
  console.log('Request Failed ' + reason)
})// /EXAMPLE 1


/**
 * EXAMPLE2: 在 Promise 的 callback 中回傳另一個 Promise
 * 留意這裡的 waitASecond 前面有使用 `return`
 **/

function waitASecond(seconds) {
	console.log('start', seconds)
  return new Promise((resolve, reject) => {
    setTimeout(function() {
      seconds++
      resolve(seconds)
    }, 1000)
  })
}

waitASecond(0)
  .then((seconds) => {
  	console.log('In first .then', seconds)
  	return waitASecond(seconds) 
  })
  .then((seconds) => {
    console.log('In second .then', seconds)
    return waitASecond(seconds)
  })
   .then((seconds) => {
    console.log('In third .then', seconds)
  })// /EXAMPLE 2