## 递归终止的条件 ``` if (arr.length <= 1) { return arr } ``` ``` function quickSort (arr) { if (arr.length <= 1) { return arr } let pivotIndex = Math.floor(arr.length / 2) // 注意 let pivot = arr.splice(pivotIndex, 1)[0] let left = [] let right = [] for (let i = 0; i < arr.length; i++) { if (arr[i] < pivot) { left.push(arr[i]) } else { right.push(arr[i]) } } // 递归 return quickSort(left).concat([pivot], quickSort(right)) } ```