reduce 函数 20 个高级用法 看看你掌握了多少？

reduce(callbackFn)reduce(callbackFn, initialValue)

const sum = (arr) => arr.reduce((acc, cur) => acc + cur, 0);//累计值为acc//当前值为cur//初始值为initialValue 为0let arr = [1, 2, 3, 4, 5];console.log("参数为：", arr);console.log("总和为：", sum(arr));

const product = (arr) => arr.reduce((acc, curr) => acc * curr, 1);let arr1 = [1, 2, 3, 4, 5];console.log("参数为：", arr1);console.log("乘积为：", product(arr1));

const flatten = (arr) => arr.reduce((acc, curr) => acc.concat(curr), []);let arr = [[1, 2], [3, 4], [5]];console.log("参数为：", arr);console.log("结果为：", flatten(arr));

const average = (arr) => arr.reduce((acc, curr) => acc + curr, 0) / arr.length;let arr = [1, 2, 3, 4, 5];console.log("参数为：", arr);console.log("结果为：", average(arr));

const max = (arr) => arr.reduce((acc, curr) => Math.max(acc, curr), Number.NEGATIVE_INFINITY);let arr = [1, 2, 3, 4, 5];console.log("参数为：", arr);console.log("结果为：", max(arr));

const min = (arr) => arr.reduce((acc, curr) => Math.min(acc, curr), Number.POSITIVE_INFINITY);let arr = [1, 2, 3, 4, 5];console.log("参数为：", arr);console.log("结果为：", min(arr));

const factorial = (n) => Array.from({ length: n }, (_, i) => i + 1).reduce((acc, curr) => acc * curr, 1);//  Array.from({ length: n }, (_, i) => i + 1) 生成数组数据 [1,2,3,4,5]console.log("参数为：", 5);console.log("结果为：", factorial(5));

const unique = (arr) => arr.reduce((acc, curr) => acc.includes(curr) ? acc : [...acc, curr], []);let arr = [1, 2,3,4,2, 3, 4, 5];console.log("参数为：", arr);console.log("结果为：", unique(arr));

const countOccurrences = (arr) => arr.reduce((acc, curr) => {    acc[curr] = (acc[curr] || 0) + 1;    return acc;}, {});
let arr = [1, 2,3,4,2, 3, 4, 5];console.log("参数为：", arr);console.log("结果为：", countOccurrences(arr));

const union = (...arrays) => arrays.reduce((acc, curr) => [...new Set([...acc, ...curr])], []);
let arr = [1, 2,3,4,2, 3, 4, 5];let arr1 = [1, 2, 3, 4, 5];console.log("参数为：", arr,arr1);console.log("结果为：", union(arr,arr1));

const intersection = (...arrays) => arrays.reduce((acc, curr) => acc.filter(value => curr.includes(value)));
let arr = [1, 2,3,4,2, 3, 4, 5];let arr1 = [1, 2, 3, 4, 5];console.log("参数为：", arr,arr1);console.log("结果为：", intersection(arr,arr1));

const difference = (arr1, arr2) => arr1.reduce((acc, curr) => arr2.includes(curr) ? acc : [...acc, curr], []);
let arr = [1, 2,3,4,2, 3, 4, 5,9];let arr1 = [1, 2, 3, 4, 5,7,8];console.log("参数为：", arr,arr1);console.log("结果为：", difference(arr,arr1));

const difference = (arr1, arr2) => arr1.reduce((acc, curr) => arr2.includes(curr) ? acc : [...acc, curr], []);const symmetricDifference = (arr1, arr2) => [...difference(arr1, arr2), ...difference(arr2, arr1)];let arr = [1, 2,3,4,2, 3, 4, 5,9];let arr1 = [1, 2, 3, 4, 5,7,8];console.log("参数为：", arr,arr1);console.log("结果为：", symmetricDifference(arr,arr1));

const chunk = (arr, size) => arr.reduce((acc, _, i) => i % size === 0 ? [...acc, arr.slice(i, i + size)] : acc, []);
let arr = [1, 2,3,4,2, 3, 4, 5,9];console.log("参数为：", arr);console.log("结果为：", chunk(arr,4));

const groupBy = (arr, key) => arr.reduce((acc, obj) => {    const groupKey = obj[key];    acc[groupKey] = [...(acc[groupKey] || []), obj];    return acc;}, {});
let arr = [{ id: 1, name: '微芒不朽' }, { id: 2, name: '微芒' }, { id: 1, name: '微芒不朽' }];console.log("参数为：", arr);console.log("结果为：", groupBy(arr,"name"));

// 16. 数组去除假值const compact = (arr) => arr.reduce((acc, curr) => curr ? [...acc, curr] : acc, []);let arr = [0, 1, false, 2, '', 3]console.log("参数为：", arr);console.log("结果为：", compact(arr,"name"));

const removeEmpty = (arr) => arr.reduce((acc, curr) => curr ? [...acc, curr] : acc, []);
let arr = [0, 1, null, 2,undefined, '', 3]console.log("参数为：", arr);console.log("结果为：", removeEmpty(arr,"name"));

const removeItem = (arr, item) => arr.reduce((acc, curr) => curr === item ? acc : [...acc, curr], []);let arr = [1, 2, 3, 4, 2, 5]console.log("参数为：", arr);console.log("结果为：", removeItem(arr,2));

const mapArray = (arr, fn) => arr.reduce((acc, curr) => [...acc, fn(curr)], []);let arr = [1, 2, 3, 4, 2, 5]console.log("参数为：", arr,(x)=>x+2);console.log("结果为：", mapArray(arr,(x)=>x+2));

const filterArray = (arr, fn) => arr.reduce((acc, curr) => fn(curr) ? [...acc, curr] : acc, []);let arr = [1, 2, 3, 4, 2, 5]console.log("参数为：", arr,(x) => x % 2 === 0);console.log("结果为：", filterArray(arr,(x) => x % 2 === 0));

function randomColor() {  let r = Math.floor(Math.random()*256);  let g = Math.floor(Math.random()*256);  let b = Math.floor(Math.random()*256);  //返回随机生成的颜色  return "rgb("+r+","+g+","+b+")";}console.log = (function(oriLogFunc){  return function(...data)  {    const icons = ["🌵", "🎍", "🐾", "🌀", "🐚", "🥝", "🥜", "🥕", "🥒", "🌽", "🍒", "🍅", "🍑", "🍋", "🍈", "🌶", "🌰", "🍠", "🍆", "🍄", "🍐", "🍌", "🍍", "🍇", "🍏", "🍓", "🍎", "🍊", "🐴", "🐗", "🦄", "🐑", "🐶", "🐔", "🐼", "🐒", "🌝", "💄", "💋", "👠", "👗", "👙", "🧣", "🍰", "🍭", "🍳", "🎄", "🎱", "⚽", "🏀", "🎵", "🚄", "⭕", "❌", "❓", "❗", "💯"]    const icon = icons[Math.floor(Math.random() * icons.length)];    const bgColor = randomColor()    const color = randomColor()    oriLogFunc.call(console,`%c ${icon} `, `border-radius:5px;padding:12px;border:1px solid #000;color: #43bb88;font-size: 16px;font-weight: bold;text-decoration: underline;`, ...data);  }})(console.log);