1. 数组排序

1.1 冒泡排序

  1. //将第一个值与身后相邻的值进行比较，若身后相邻的值小则与第一个值交换位置。
  2. const arr = [11, 33, -5, 17, 3, 59, 259, -39, 152];
  4. for (var i = 0; i <= arr.length - 1; i++) {
  5.   for (var j = 0; j <= arr.length - i - 1; j++) {
  6.     if (arr[j] > arr[j + 1]) {
  7.       var temp = arr[j]
  8.       arr[j] = arr[j + 1]
  9.       arr[j + 1] = temp
  10.     }
  11.   }
  12. }
  13. console.log(arr)

2. 选择排序

  • 首先在未排序序列中找到最小的元素，存放在排序序列的起始位置。
  • 再从剩余未排序元素中继续寻找最小元素，然后放在已经排序列的末尾
  • 重复以上步骤.
    1. var arr = [10, 90, 55, 96, 23, 8, 79];
    2. for (var i = 0; i < arr.length - 1; i++) {
    3. var minIndex = i;
    4. for (var j = i + 1; j < arr.length; j++) {
    5.   if (arr[j] > arr[minIndex]) {
    6.     minIndex = j
    7.   }
    8. }
    9. const temp = arr[i];
    10. arr[i] = arr[minIndex]
    11. arr[minIndex] = temp
    12. }

    1.2 sort排序

    1. const arr = [11, 33, -5, 17, 3, 59, 259, -39, 152];
    2. arr.sort((a, b) => {
    3. return a - b
    4. })
    5. console.log('2', arr)

    2. 数组去重

    ```javascript //第一种 new Set() const arr1 = [11, 22, 33, 14, 22, 33] const arr2 = […new Set(arr1)] console.log(arr2) //[11, 22, 33, 14]

//第二种 indexOf const arr1 = [11, ‘a’, 22, 33, 14, 22, 33, ‘a’, null] let arr2 = [] arr1.forEach(item => { //如果检索的字符串值没有出现， 则返回-1 if (arr2.indexOf(item) == -1) { arr2.push(item) } }) console.log(arr2) //[11, ‘a’, 22, 33, 14, null]

//第三种 includes const arr1 = [11, ‘a’, 22, 33, 14, 22, 33, ‘a’, null] let arr2 = [] arr1.forEach(item => { //如果检索的字符串值没有出现， 则返回-1 if (!arr2.includes(item)) { arr2.push(item) } }) console.log(arr2) //[11, ‘a’, 22, 33, 14, null]

//第四种 reduce + includes const arr1 = [11, ‘a’, 22, 33, 14, 22, 33, ‘a’, null,33] let arr2 = arr1.reduce((prev, cur) => prev.includes(cur) ? prev : […prev, cur], [])

console.log(arr2) //[11, ‘a’, 22, 33, 14, null]

//第五种 reduce + indexOf const arr1 = [11, ‘a’, 22, 33, 14, 22, 33, ‘a’, null] let arr2 = arr1.reduce((prev, cur) => prev.indexOf(cur) !== -1 ? prev : […prev, cur], [])

console.log(arr2) //[11, ‘a’, 22, 33, 14, null]

//第六种 filter + indexOf const arr1 = [11, ‘a’, 22, 33, 14, 22, 11, ‘a1’, null] let arr2 = arr1.filter((item, index, arr) => { //当前元素，在原始数组中的第一个索引==当前索引值，否则返回当前元素 return arr.indexOf(item, 0) === index })

console.log(arr2) //[11, ‘a’, 22, 33, 14, ‘a1’,null]

  1. ```javascript
  2. var arr = [
  3.     {
  4.       key: '01',
  5.       value: '乐乐',
  6.     },
  7.     {
  8.       key: '02',
  9.       value: '博博',
  10.     },
  11.     {
  12.       key: '03',
  13.       value: '淘淘',
  14.     },
  15.     {
  16.       key: '04',
  17.       value: '哈哈',
  18.     },
  19.     {
  20.       key: '01',
  21.       value: '乐乐',
  22.     },
  23.   ]
  25. //第一种方法  
  26.   let obj = {};
  27.   for (var i = 0; i < arr.length; i++) {
  28.     obj[arr[i]['key']] = arr[i]
  29.   }
  30.   console.log(Object.values(obj))
  32. //第二种方式
  33. let obj = {};
  34. let resData = []
  35. arr.forEach(item => {
  36.   if (!obj[item['key']]) {
  37.     resData.push(item)
  38.     obj[item['key']] = true
  39.   }
  40. })
  42. //第三种
  43. const obj = new Map();
  44. const resData = arr.filter(item => !obj.has(item['key']) && obj.set(item['key'], 1))
  45. console.log(resData)
  47. //第四种
  48. let resData = []
  49. arr.forEach((item, index) => {
  50.   //findIndex作用：找到遍历的数组中的第一个符合判断条件的值，并返回该值对应的索引，停止遍历
  51.   const findIndex = arr.findIndex(each => each.key === item.key)
  52.   if (findIndex === index) {
  53.     resData.push(item)
  54.   }
  55. })