TypeError：arr.reduce不是一个函数

Question

我在刷新应用程序时不时收到此错误消息，我正在建立一个反应难题，但找不到我所缺少或写错的东西吗？谁能帮我写些什么？

错误消息：TypeError: arr.reduce is not a function flattenArray

const flattenArray = arr => {
  return arr.reduce((flatArr, subArr) => flatArr.concat(subArr), []);
};

代码：

const getShuffledPuzzle = () => {
  const values = [0, 1, 2, 3, 4, 5, 6, 7, 8];

  const rowOne = [],
    rowTwo = [],
    rowThree = [];

  while (values.length) {
    const random = Math.floor(Math.random() * values.length)

    if (rowOne.length < 3) {
      rowOne.push(values.splice(random, 1)[0])
    } else if (rowTwo.length < 3) {
      rowTwo.push(values.splice(random, 1)[0])
    } else {
      rowThree.push(values.splice(random, 1)[0])
    }
  }
  return [rowOne, rowTwo, rowThree]
}

这是我收到TypeError的地方：

const flattenArray = (arr) => {
  return arr.reduce((flatArr, subArr) => flatArr.concat(subArr), [])
};

const getInversionCount = arr => {
  arr = flattenArray(arr).filter(n => n !== 0)
  const inversions = [];

  for (let i = 0; i < arr.length - 1; i++) {
    const currentValue = arr[i]
    const currentInversions = arr.filter(
      (val, j) => i < j && val < currentValue
    )
    inversions.push(currentInversions.length)
  }

  const inversionsCount = inversions.reduce((total, val) => total + val, 0)

  return inversionsCount
}

const isSolvable = puzzle => {
  return getInversionCount(puzzle) % 2 === 0
};

const getPuzzle = () => {
  let puzzle = getShuffledPuzzle()

  while (!isSolvable(puzzle)) {
    puzzle = getShuffledPuzzle
  }
  return puzzle
}


````

Answer 1

const flattenArray = (arr = []) => arr.reduce((flatArr, subArr) => flatArr.concat(subArr), [])