13. 控制循环暂停和恢复

// ES5 无法控制循环的暂停和恢复
function loop () {
  for (let i = 0; i < 5; i++) {
    console.log(i)
  }
}
// ES6
loop()
function * loop () {
  for (let i = 0; i < 5; i++) {
    yield console.log(i)
  }
}

const l = loop()

l.next()
l.next()
l.next()
l.next()
l.next()
l.next()
l.next()

function * gen () {
  let val
  val = yield 1
  console.log(val)
}

const l = gen()
l.next()
l.next()
function * gen () {
  let val
  val = yield * [1, 2, 3]
  console.log(val)
}

const l = gen()
{
  next(){
    value:1,
    done:false
  }
}
console.log(l)
console.log(l.next())
console.log(l.next())
function * gen () {
  let val
  val = (yield [1, 2, 3]) + 7
  console.log(val)
}

const l = gen()
console.log(l.next(10))
console.log(l.return(100))
console.log(l.next(20))

抛出错误

function * gen () {
  while (true) {
    try {
      yield 1
    } catch (e) {
      console.log(e.message)
    }
  }
}

const g = gen()
console.log(g.next())
console.log(g.next())
console.log(g.next())
console.log(g.next())
g.throw(new Error('ss'))
console.log(g.next())

模拟抽奖

// ES5
function draw (first = 1, second = 3, third = 5) {
  let firstPrize = ['1A', '1B', '1C', '1D', '1E']
  let secondPrize = ['2A', '2B', '2C', '2D', '2E', '2F', '2G', '2H', '2I']
  let thirdPrize = ['3A', '3B', '3C', '3D', '3E', '3F', '3G', '3K', '3O', '3P']
  let result = []
  let random
  // 抽一等奖
  for (let i = 0; i < first; i++) {
    random = Math.floor(Math.random() * firstPrize.length)
    result = result.concat(firstPrize.splice(random, 1))
  }
  // 抽二等奖
  for (let i = 0; i < second; i++) {
    random = Math.floor(Math.random() * secondPrize.length)
    result = result.concat(secondPrize.splice(random, 1))
  }
  // 抽三等奖
  for (let i = 0; i < third; i++) {
    random = Math.floor(Math.random() * thirdPrize.length)
    result = result.concat(thirdPrize.splice(random, 1))
  }
  return result
}

//ES6

let t = draw()
for (let value of t) {
  console.log(value)
}
function * draw (first = 1, second = 3, third = 5) {
  let firstPrize = ['1A', '1B', '1C', '1D', '1E']
  let secondPrize = ['2A', '2B', '2C', '2D', '2E', '2F', '2G', '2H', '2I']
  let thirdPrize = ['3A', '3B', '3C', '3D', '3E', '3F', '3G', '3K', '3O', '3P']
  let count = 0
  let random

  while (1) {
    if (count < first) {
      random = Math.floor(Math.random() * firstPrize.length)
      yield firstPrize[random]
      count++
      firstPrize.splice(random, 1)
    } else if (count < first + second) {
      random = Math.floor(Math.random() * secondPrize.length)
      yield secondPrize[random]
      count++
      secondPrize.splice(random, 1)
    } else if (count < first + second + third) {
      random = Math.floor(Math.random() * thirdPrize.length)
      yield thirdPrize[random]
      count++
      thirdPrize.splice(random, 1)
    } else {
      return false
    }
  }
}

let d = draw()
console.log(d.next().value)
console.log(d.next().value)
console.log(d.next().value)
console.log(d.next().value)
console.log(d.next().value)
console.log(d.next().value)
console.log(d.next().value)
console.log(d.next().value)
console.log(d.next().value)
console.log(d.next().value)

模拟游戏

function * count (x = 1) {
  while (1) {
    if (x % 3 === 0) {
      yield x
    }
    x++
  }
}

let num = count()
console.log(num.next().value)
console.log(num.next().value)
console.log(num.next().value)
console.log(num.next().value)
console.log(num.next().value)
console.log(num.next().value)
console.log(num.next().value)
console.log(num.next().value)
console.log(num.next().value)

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