// Anagrams of string
const anagrams = str => {
if (str.length <= 2) return str.length === 2 ? [str, str[1] + str[0]] : [str];
return str.split('').reduce((acc, letter, i) =>
acc.concat(anagrams(str.slice(0, i) + str.slice(i + 1)).map(val => letter + val)), []);
};
// anagrams('abc') -> ['abc','acb','bac','bca','cab','cba']
//数组平均数
const average = arr => arr.reduce((acc, val) => acc + val, 0) / arr.length;
// 大写每个单词的首字母
const capitalizeEveryWord = str => str.replace(/\b[a-z]/g, char => char.toUpperCase());
//首字母大写
const capitalize = (str, lowerRest = false) =>
str.slice(0, 1).toUpperCase() + (lowerRest ? str.slice(1).toLowerCase() : str.slice(1));
// capitalize(‘myName’, true) -> ‘Myname’
//检查回文
const palindrome = str => {
const s = str.toLowerCase().replace(/[\W_]/g, '');
return s === s.split('').reverse().join('');
}
// palindrome('taco cat') -> true
//计数数组中值的出现次数
const countOccurrences = (arr, value) => arr.reduce((a, v) => v === value ? a + 1 : a + 0, 0);
// countOccurrences([1,1,2,1,2,3], 1) -> 3
//当前URL
const currentUrl = _ => window.location.href;
// currentUrl() -> 'https://google.com'
//Curry
const curry = (fn, arity = fn.length, ...args) =>
arity <= args.length ? fn(...args) : curry.bind(null, fn, arity, ...args);
// curry(Math.pow)(2)(10) -> 1024 、curry(Math.min, 3)(10)(50)(2) -> 2
//Deep flatten array
const deepFlatten = arr => arr.reduce((a, v) => a.concat(Array.isArray(v) ? deepFlatten(v) : v), []);
// deepFlatten([1,[2],[[3],4],5]) -> [1,2,3,4,5]
//数组之间的区别
const difference = (a, b) => { const s = new Set(b); return a.filter(x => !s.has(x)); };
// difference([1,2,3], [1,2]) -> [3]
//两点之间的距离
const distance = (x0, y0, x1, y1) => Math.hypot(x1 - x0, y1 - y0);
// distance(1,1, 2,3) -> 2.23606797749979
//可以按数字整除
const isDivisible = (dividend, divisor) => dividend % divisor === 0;
// isDivisible(6,3) -> true
//转义正则表达式
const escapeRegExp = str => str.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
// escapeRegExp('(test)') -> \\(test\\)
//偶数或奇数
const isEven = num => num % 2 === 0;
// isEven(3) -> false
//阶乘
const factorial = n => n <= 1 ? 1 : n * factorial(n - 1);
// factorial(6) -> 720
//斐波那契数组生成器
const fibonacci = n =>
Array(n).fill(0).reduce((acc, val, i) => acc.concat(i > 1 ? acc[i - 1] + acc[i - 2] : i), []);
// fibonacci(5) -> [0,1,1,2,3]
//过滤数组中的非唯一值
const filterNonUnique = arr => arr.filter(i => arr.indexOf(i) === arr.lastIndexOf(i));
// filterNonUnique([1,2,2,3,4,4,5]) -> [1,3,5]
//Flatten数组
const flatten = arr => arr.reduce((a, v) => a.concat(v), []);
// flatten([1,[2],3,4]) -> [1,2,3,4]
//从数组中获取最大值
const arrayMax = arr => Math.max(...arr);
// arrayMax([10, 1, 5]) -> 10
//从数组中获取最小值
const arrayMin = arr => Math.min(...arr);
// arrayMin([10, 1, 5]) -> 1
//获取滚动位置
const getScrollPos = (el = window) =>
({
x: (el.pageXOffset !== undefined) ? el.pageXOffset : el.scrollLeft,
y: (el.pageYOffset !== undefined) ? el.pageYOffset : el.scrollTop
});
// getScrollPos() -> {x: 0, y: 200}
//最大公约数（GCD）
const gcd = (x, y) => !y ? x : gcd(y, x % y);
// gcd (8, 36) -> 4
//Head of list
const head = arr => arr[0];
// head([1,2,3]) -> 1
//list初始化
const initial = arr => arr.slice(0, -1);
// initial([1,2,3]) -> [1,2]
//用range初始化数组
const initializeArrayRange = (end, start = 0) =>
Array.apply(null, Array(end - start)).map((v, i) => i + start);
// initializeArrayRange(5) -> [0,1,2,3,4]
//用值初始化数组
const initializeArray = (n, value = 0) => Array(n).fill(value);
// initializeArray(5, 2) -> [2,2,2,2,2]
//列表的最后
const last = arr => arr.slice(-1)[0];
// last([1,2,3]) -> 3
// 测试功能所花费的时间
const timeTaken = callback => {
console.time('timeTaken');
const r = callback();
console.timeEnd('timeTaken');
return r;
};
// timeTaken(() => Math.pow(2, 10)) -> 1024
// (logged): timeTaken: 0.02099609375ms
//来自键值对的对象
const objectFromPairs = arr => arr.reduce((a, v) => (a[v[0]] = v[1], a), {});
// objectFromPairs([['a',1],['b',2]]) -> {a: 1, b: 2}
//管道-使用Array.reduce（）通过函数传递值。
const pipe = (...funcs) => arg => funcs.reduce((acc, func) => func(acc), arg);
// pipe(btoa, x => x.toUpperCase())("Test") -> "VGVZDA=="
//Powerset-使用reduce（）与map（）结合来遍历元素，并将其组合成包含所有组合的数组。
const powerset = arr =>
arr.reduce((a, v) => a.concat(a.map(r => [v].concat(r))), [[]]);
// powerset([1,2]) -> [[], [1], [2], [2,1]]
//范围内的随机整数
const randomIntegerInRange = (min, max) => Math.floor(Math.random() * (max - min + 1)) + min;
// randomIntegerInRange(0, 5) -> 2
//范围内的随机数
const randomInRange = (min, max) => Math.random() * (max - min) + min;
// randomInRange(2,10) -> 6.0211363285087005
//随机化数组的顺序
const shuffle = arr => arr.sort(() => Math.random() - 0.5);
// shuffle([1,2,3]) -> [2,3,1]
//重定向到URL
const redirect = (url, asLink = true) =>
asLink ? window.location.href = url : window.location.replace(url);
// redirect('https://google.com')
//反转一个字符串
const reverseString = str => [...str].reverse().join('');
// reverseString('foobar') -> 'raboof'
//RGB到十六进制
const rgbToHex = (r, g, b) => ((r << 16) + (g << 8) + b).toString(16).padStart(6, '0');
// rgbToHex(255, 165, 1) -> 'ffa501'
//滚动到顶部
const scrollToTop = _ => {
const c = document.documentElement.scrollTop || document.body.scrollTop;
if (c > 0) {
window.requestAnimationFrame(scrollToTop);
window.scrollTo(0, c - c / 8);
}
};
// scrollToTop()
//随机数组值
const shuffle = arr => {
let r = arr.map(Math.random);
return arr.sort((a, b) => r[a] - r[b]);
}
// shuffle([1, 2, 3] -> [2, 1, 3])
//数组之间的相似性
const similarity = (arr, values) => arr.filter(v => values.includes(v));
// similarity([1,2,3], [1,2,4]) -> [1,2]
//按字符串排序（按字母顺序排列）
const sortCharactersInString = str =>
str.split('').sort((a, b) => a.localeCompare(b)).join('');
// sortCharactersInString('cabbage') -> 'aabbceg'
//数组总和
const sum = arr => arr.reduce((acc, val) => acc + val, 0);
// sum([1,2,3,4]) -> 10
// 交换两个变量的值
[varA, varB] = [varB, varA];
// [x, y] = [y, x]
//列表的tail
const tail = arr => arr.length > 1 ? arr.slice(1) : arr;
// tail([1,2,3]) -> [2,3]
// tail([1]) -> [1]
// 数组唯一值
const unique = arr => [...new Set(arr)];
// unique([1,2,2,3,4,4,5]) -> [1,2,3,4,5]
//URL参数
const getUrlParameters = url =>
url.match(/([^?=&]+)(=([^&]*))/g).reduce(
(a, v) => (a[v.slice(0, v.indexOf('='))] = v.slice(v.indexOf('=') + 1), a), {}
);
// getUrlParameters('http://url.com/page?name=Adam&surname=Smith') -> {name: 'Adam', surname: 'Smith'}
//UUID生成器
const uuid = _ =>
([1e7] + -1e3 + -4e3 + -8e3 + -1e11).replace(/[018]/g, c =>
(c ^ crypto.getRandomValues(new Uint8Array(1))[0] & 15 >> c / 4).toString(16)
);
// uuid() -> '7982fcfe-5721-4632-bede-6000885be57d'
// 验证数字
const validateNumber = n => !isNaN(parseFloat(n)) && isFinite(n) && Number(n) == n;
// validateNumber('10') -> true
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