1. /* 休眠函数 */
    2. const sleep = (timeout = 2000) => {
    3.   return new Promise((resolve) => {
    4.     setTimeout(() => resolve([]), timeout);
    5.   })
    6. }
    8. /* 数组 reduce() 的各种用法 */
    9. /* 累加，累乘 */
    10. function Accumulation(...vals) {
    11.   return vals.reduce((t, c) => t + c, 0)
    12. }
    13. function Multiplication(...vals) {
    14.   return vals.reduce((t, c) => t * c, 1)
    15. }
    16. // console.log(`累加`, Accumulation(1, 2, 3)) // 累加 6
    17. // console.log(`累乘`, Multiplication(1, 2, 3)) // 累乘 6
    19. /* 权重求和 */
    20. var scores = [
    21.   { score: 90, subject: "chinese", weight: 0.5 },
    22.   { score: 95, subject: "math", weight: 0.3 },
    23.   { score: 85, subject: "english", weight: 0.2 }
    24. ]
    25. var result = scores.reduce((t, c) => t + c.score * c.weight, 0) // 90.5
    27. /* 
    28.   代替reverse
    29.     逗号操作符  对它的每个操作数求值（从左到右），并返回最后一个操作数的值。
    30. */
    31. function Reverse(list = []) {
    32.   // return list.reduce((t, c) => (t.unshift(c), t), [])
    33.   return list.reduceRight((t, c) => (t.push(c), t), [])
    34. }
    35. // console.log(Reverse([12, 34, 56])) // [ 56, 34, 12 ]
    37. /* 代替map和filter */
    38. var arr = [0, 1, 2, 3];
    40. // 代替map：[0, 2, 4, 6]
    41. var a = arr.map(i => i * 2)
    42. var b = arr.reduce((t, c) => [...t, c * 2], [])
    44. // 代替filter：[2, 3]
    45. var c = arr.filter(i => i > 1)
    46. var d = arr.reduce((t, c) => c > 1 ? [...t, c] : t, [])
    48. // 代替map和filter：[4, 6]
    49. var e = arr.map(i => i * 2).filter(i => i > 2)
    50. var f = arr.reduce((t, c) => c * 2 > 2 ? [...t, c * 2] : t, [])
    52. /* 代替some和every */
    53. var scores = [
    54.   { score: 45, subject: "chinese" },
    55.   { score: 90, subject: "math" },
    56.   { score: 60, subject: "english" }
    57. ]
    58. // 代替some：至少一门合格
    59. var isAtLeastOneQualified = scores.reduce((t, c) => t || c.score >= 60, false) // true
    60. // 代替every：全部合格
    61. var isAllQualified = scores.reduce((t, c) => t && c.score >= 60, true) // false
    64. /* 数组分割 */
    65. var arr = [1, 2, 3, 4, 5]
    66. function Chunk(arr = [], size = 1) {
    67.   return arr.length
    68.     ? arr.reduce(
    69.       (t, v) => (
    70.         t[t.length - 1].length === size ? t.push([v]) : t[t.length - 1].push(v), t
    71.       ), [[]]
    72.     )
    73.     : [];
    74. }
    75. // console.log(Chunk(arr, 2)) // [ [ 1, 2 ], [ 3, 4 ], [ 5 ] ]
    78. /* 
    79.   数组过滤
    80.   两个数组，参照某个数组过滤另一个数组
    81.   代码中：交集
    82.   扩展：并集、差集
    83. */
    84. var arr1 = [1, 2, 3, 4]
    85. var arr2 = [2, 3, 7, 8]
    86. function Difference(arr = [], oarr = []) {
    87.   return arr.reduce((t, c) => (oarr.includes(c) && t.push(c), t), [])
    88. }
    89. // console.log(Difference(arr1, arr2)) // [ 2, 3 ]
    92. /* 
    93.   数组填充
    94.   替换数组中指定位置元素
    95. */
    96. function Fill(arr = [], val = '', start = 0, end = arr.length) {
    97.   if (start < 0 || start >= end || end > arr.length) return arr
    98.   return [
    99.     ...arr.slice(0, start),
    100.     ...arr.slice(start, end).reduce((t, c) => (t.push(val || c), t), []),
    101.     ...arr.slice(end, arr.length)
    102.   ]
    103. }
    104. var arr = [0, 1, 2, 3, 4, 5, 6]
    105. // console.log(JSON.stringify(Fill(arr, 'aaa', 1, 5))) // [0,"aaa","aaa","aaa","aaa",5,6]
    108. /* 数组扁平 */
    109. function Flat(arr = []) {
    110.   return arr.reduce((t, c) => t.concat(Array.isArray(c) ? Flat(c) : c), [])
    111. }
    114. /* 数组去重 */
    115. function Uniq(arr = []) {
    116.   return arr.reduce((t, c) => t.includes(c) ? t : [...t, c], [])
    117. }
    120. /* 数组最大最小值 */
    121. function Max(arr = []) {
    122.   return arr.reduce((t, c) => t > c ? t : c)
    123. }
    124. function Min(arr = []) {
    125.   return arr.reduce((t, c) => t < c ? t : c)
    126. }
    127. var arr = [12, 45, 21, 65, 38, 76, 108, 43];
    128. // console.log(Max(arr), Min(arr)) // 108 12
    131. /* 数组成员独立拆解 */
    132. var arr = [['a', 1, true], ['b', 2, false]] // [['a', 'b'], [1, 2], [true, false]]
    133. function Unzip(arr = []) {
    134.   return arr.reduce(
    135.     (t, c) => (c.forEach((item, index) => t[index].push(item)), t),
    136.     Array.from({ length: Math.max(...arr.map(c => c.length)) }).map(() => [])
    137.   )
    138. }
    141. /* 数组成员的个数统计 */
    142. function Count(arr = []) {
    143.   return arr.reduce((t, c) => (t[c] = (t[c] || 0) + 1, t), {})
    144. }
    147. /* 数组成员位置记录 */
    148. var arr = [2, 1, 5, 4, 2, 1, 6, 6, 7] // [ 0, 4 ]
    149. function Position(arr = [], target) {
    150.   return arr.reduce((t, c, i) => (c === target && t.push(i), t), [])
    151. }
    154. /* 数组成员特性分组 */
    155. var arr = [
    156.   { area: "GZ", name: "YZW", age: 27 },
    157.   { area: "GZ", name: "TYJ", age: 25 },
    158.   { area: "SZ", name: "AAA", age: 23 },
    159.   { area: "FS", name: "BBB", age: 21 },
    160.   { area: "SZ", name: "CCC", age: 19 }
    161. ]; // 以地区area作为分组依据
    162. // Group(arr, "area") 结果是： { GZ: Array(2), SZ: Array(2), FS: Array(1) }
    163. function Group(arr = [], key) {
    164.   return key ? arr.reduce((t, c) => (!t[c[key]] && (t[c[key]] = []), t[c[key]].push(c), t), {}) : {}
    165. }
    168. /* 数组成员所含关键字统计 */
    169. var text = [
    170.   "今天天气真好，我想出去钓鱼",
    171.   "我一边看电视，一边写作业",
    172.   "小明喜欢同桌的小红，又喜欢后桌的小君，真TM花心",
    173.   "最近上班喜欢摸鱼的人实在太多了，代码不好好写，在想入非非"
    174. ];
    175. var keyword = ["偷懒", "喜欢", "睡觉", "摸鱼", "真好", "一边", "明天"];
    176. // Keyword(text, keyword); // ["喜欢", "摸鱼", "真好", "一边"]
    177. function Keyword(arr = [], keys = []) {
    178.   return keys.reduce((t, c) => (arr.some(w => w.includes(c)) && t.push(c), t), [])
    179. }
    182. /* 字符串翻转 */
    183. var str = "reduce最牛逼";
    184. // ReverseStr(str); // "逼牛最ecuder"
    185. function ReverseStr(str) {
    186.   return str.split('').reduceRight((t, c) => t + c)
    187. }
    190. /* 
    191.   ! 数字千分化
    192. */
    193. // ThousandNum(1234); // "1,234"
    194. // ThousandNum(1234.00); // "1,234"
    195. // ThousandNum(0.1234); // "0.123,4"
    196. // ThousandNum(1234.5678); // "1,234.567,8"
    197. function ThousandNum(num = 0) {
    198.   const str = (+num).toString().split('.')
    199.   const int = nums => nums.split('').reverse().reduceRight((t, c, i) => t + (i % 3 ? c : `${c},`), '').replace(/^,|,$/g, '')
    200.   const dec = nums => nums.split('').reduce((t, c, i) => t + ((i + 1) % 3 ? c : `${c},`), '').replace(/^,|,$/g, '')
    201.   return str.length > 1 ? `${int(str[0])}.${dec(str[1])}` : int(str[0])
    202. }
    204. /* 
    205.   ! 异步累计
    206. */
    207. // const result = await AsyncTotal(); // 需要在async包围下使用
    208. async function AsyncTotal(arr = []) {
    209.   return arr.reduce(async(t, c) => {
    210.     const at = await t;
    211.     const todo = await Todo(c);
    212.     at[c] = todo;
    213.     return at
    214.   }, Promise.resolve({}))
    215. }
    216. async function name(params) {
    217.   const result = await AsyncTotal()
    218.   console.log(result)
    219. }
    222. /* 斐波那契数列 */
    223. // Fibonacci(10); // [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]
    224. function Fibonacci(len = 2) {
    225.   const arr = [...new Array(len).keys()]
    226.   return arr.reduce((t, c, i) => (i > 1 && t.push(t[i - 1] + t[i - 2]), t), [0, 1])
    227. }
    230. /* URL参数反序列化 */
    231. // 假设URL为：https://www.baidu.com?age=25&name=TYJ
    232. // ParseUrlSearch(); // { age: "25", name: "TYJ" }
    233. function ParseUrlSearch() {
    234.   return location.search.replace(/(^\?)|(&$)/g, '').split('&').reduce((t, c) => {
    235.     const [key, value] = c.split('=')
    236.     t[key] = decodeURIComponent(value)
    237.     return t
    238.   }, {})
    239. }
    242. /* URL参数序列化 */
    243. // StringifyUrlSearch({ age: 27, name: "YZW" }); // "?age=27&name=YZW"
    244. function StringifyUrlSearch(search = {}) {
    245.   return Object.entries(search).reduce(
    246.     (t, c) => `${t}${c[0]}=${encodeURIComponent(c[1])}&`,
    247.     Object.keys(search).length ? '?' : ''
    248.   ).replace(/&?/, '');
    249. }
    252. /* 返回对象指定键值 */
    253. var target = { a: 1, b: 2, c: 3, d: 4 };
    254. var keyword = ["a", "d"];
    255. // GetKeys(target, keyword); // { a: 1, d: 4 }
    256. function GetKeys(obj = {}, keys = []) {
    257.   return Object.keys(obj).reduce((t, c) => (keys.includes(c) && (t[c] = obj[c]), t), {})
    258. }
    261. /* 数组转对象 */
    262. var people = [
    263.   { area: "GZ", name: "YZW", age: 27 },
    264.   { area: "SZ", name: "TYJ", age: 25 }
    265. ];
    266. // {"YZW":{"area":"GZ","age":27},"TYJ":{"area":"SZ","age":25}}
    267. function ArrayToObject(arr = []) {
    268.   if (!arr.length) return {}
    269.   return arr.reduce((t, c) => {
    270.     const { name, ...rest } = c
    271.     t[name] = rest
    272.     return t
    273.   }, {})
    274. }
    277. /* Redux Compose函数原理 */
    278. function Compose(...funs) {
    279.   if (funs.length === 0) {
    280.     return arg => arg;
    281.   }
    282.   if (funs.length === 1) {
    283.     return funs[0]
    284.   }
    285.   return funs.reduce((t, c) => (...args) => t(c(...args)))
    286. }