算法

冒泡排序

const arr = [3, 5, 6, 9, 1]

for(let i = 0; i < arr.length; i++) {
  for (let j = 0; j < arr.length - 1; j++) {
    if (arr[j] > arr[j + 1]) {
      let t = arr[j]
      arr[j] = arr[j + 1]
      arr[j + 1] = t
    }
  }
}

console.log(arr)

插入排序

const arr = [3, 5, 6, 9, 1]
const handAry = [arr[0]]

for(let i = 1; i < arr.length; i++) {
  for(let j = handAry.length - 1; j >= 0; j--) {
    if (arr[i] > handAry[j]) {
      handAry.splice(j + 1, 0, arr[i])
      break
    }
    
    if (j === 0) {
      handAry.unshift(arr[i])
    }
  }
}

console.log(handAry)

快速排序

var quickSort = function(arr) {

    if (arr.length <= 1) { return arr; }

    var pivotIndex = Math.floor(arr.length / 2);

    var pivot = arr.splice(pivotIndex, 1)[0];

    var left = [];

    var right = [];

    for (var i = 0; i < arr.length; i++){

        if (arr[i] < pivot) {

            left.push(arr[i]);

        } else {

            right.push(arr[i]);

        }

    }

    return quickSort(left).concat([pivot], quickSort(right));

};

数组打平

function flat(arr) {
  let array = []
  for (let item of arr) {
    if (Array.isArray(item)) {
      array = array.concat(...flat(item))
    } else {
      array.push(item)
    }
  }
  return array
}