递归创建从大到小排列的数组

使用递归创建从大到小排列的数组

function countdown(n) {
  if (n < 1) {
    return []
  } else {
    const arr = countdown(n - 1)
    arr.unshift(n)
    return arr
  }
}

function countdown(n) {
  if (n < 1) {
    return []
  } else {
    const arr = countdown(n - 1)
    arr.splice(0, 0, n)
    return arr
  }
}

function countdown(n) {
  return n < 1 ? [] : [n].concat(countdown(n - 1))
}

function countdown(n) {
  return n < 1 ? [] : [n, ...countdown(n - 1)]
}

使用递归创建数组范围

function rangeOfNumbers(startNum, endNum) {
  if (endNum - startNum === 0) {
    return [startNum]
  } else {
    var numbers = rangeOfNumbers(startNum, endNum - 1)
    numbers.push(endNum)
    return numbers
  }
}

function rangeOfNumbers(startNum, endNum) {
  return startNum === endNum
    ? [startNum]
    : rangeOfNumbers(startNum, endNum - 1).concat(endNum)
}

function rangeOfNumbers(startNum, endNum) {
  return startNum === endNum
    ? [startNum]
    : [...rangeOfNumbers(startNum, endNum - 1), endNum]
}