今天，我总结了 45 个强大的 JavaScript 单行代码（代码片段），这些代码在编码时经常需要用到。我根据它们的行为将它们分为多个部分。

这些 JavaScript 单行代码包括数组、对象、函数、字符串和数字操作。我尽量让它简单一点，让我们开始吧！

const flat = arr => arr.flat(Infinity);

示例：

const arr1 = [1, 2, [3, 4, [5, 6]], 7, [8, [9]]];
const arr2 = [[1], [2, [3, [4]]], [5, [6, [7]]]];
const arr3 = [[[1], [2]], [[3], [4]]];

console.log(flat(arr1)); // [1, 2, 3, 4, 5, 6, 7, 8, 9]
console.log(flat(arr2)); // [1, 2, 3, 4, 5, 6, 7]
console.log(flat(arr3)); // [1, 2, 3, 4]

const unique = arr => […new Set(arr)];

示例：

const unique = arr => [...new Set(arr)];

const arr1 = [1, 2, 2, 3, 4, 4, 5];
const arr2 = ['apple', 'banana', 'apple', 'orange'];
const arr3 = [true, false, true, false];

console.log(unique(arr1)); // [1, 2, 3, 4, 5]
console.log(unique(arr2)); // ['apple', 'banana', 'orange']
console.log(unique(arr3)); // [true, false]

const last = arr => arr[arr.length - 1 ];

示例：

const arr1 = [1, 2, 3, 4, 5];
const arr2 = ['apple', 'banana', 'orange'];
const arr3 = [true, false, true];

console.log(last(arr1)); // 5
console.log(last(arr2)); // 'orange'
console.log(last(arr3)); // true

const shuffle = arr => arr.sort(() => Math.random() - 0.5);

示例：

const arr1 = [1, 2, 3, 4, 5];
const arr2 = ['apple', 'banana', 'orange'];
const arr3 = [true, false, true];

console.log(shuffle(arr1)); // [3, 5, 2, 1, 4] (随机顺序)
console.log(shuffle(arr2)); // ['orange', 'apple', 'banana'] (随机顺序)
console.log(shuffle(arr3)); // [false, true, true] (随机顺序)

const sum = arr => arr.reduce((a, b) => a + b, 0);

示例：

const arr1 = [1, 2, 3, 4, 5];
const arr2 = [10, 20, 30];
const arr3 = [5, 5, 5];

console.log(sum(arr1)); // 15
console.log(sum(arr2)); // 60
console.log(sum(arr3)); // 15

const avg = arr => arr.reduce((a, b) => a + b, 0) / arr.length;

示例：

const arr1 = [1, 2, 3, 4, 5];
const arr2 = [10, 20, 30];
const arr3 = [5, 5, 5];

console.log(avg(arr1)); // 3
console.log(avg(arr2)); // 20
console.log(avg(arr3)); // 5

const max = arr => Math.max(...arr);

示例：

const arr1 = [1, 2, 3, 4, 5];
const arr2 = [10, 20, 30];
const arr3 = [5, 5, 5];

console.log(max(arr1)); // 5
console.log(max(arr2)); // 30
console.log(max(arr3)); // 5

const min = arr => Math.min(...arr);

示例：

const arr1 = [1, 2, 3, 4, 5];
const arr2 = [10, 20, 30];
const arr3 = [5, 5, 5];

console.log(min(arr1)); // 1
console.log(min(arr2)); // 10
console.log(min(arr3)); // 5

const intersect = (a, b) => a.filter(v => b.includes(v));

示例：

const arr1 = [1, 2, 3, 4, 5];
const arr2 = [4, 5, 6, 7, 8];
const arr3 = [1, 2, 3];
const arr4 = [3, 4, 5];

console.log(intersect(arr1, arr2)); // [4, 5]
console.log(intersect(arr1, arr3)); // [1, 2, 3]
console.log(intersect(arr3, arr4)); // [3]

const diff = (a, b) => a.filter(v => !b.includes(v));

示例：

const arr1 = [1, 2, 3, 4, 5];
const arr2 = [4, 5, 6, 7, 8];
const arr3 = [1, 2, 3];
const arr4 = [3, 4, 5];

console.log(diff(arr1, arr2)); // [1, 2, 3]
console.log(diff(arr1, arr3)); // [4, 5]
console.log(diff(arr3, arr4)); // [1, 2]

const merge = (a, b) => ({ …a, …b });

示例：

const obj1 = { a: 1, b: 2 };
const obj2 = { c: 3, d: 4 };
const obj3 = { e: 5, f: 6 };
const obj4 = { g: 7, h: 8 };

console.log(merge(obj1, obj2)); // { a: 1, b: 2, c: 3, d: 4 }
console.log(merge(obj1, obj3)); // { a: 1, b: 2, e: 5, f: 6 }
console.log(merge(obj3, obj4)); // { e: 5, f: 6, g: 7, h: 8 }

const clone = obj => ({ …obj });

示例：

const obj1 = { a: 1, b: 2 };
const obj2 = { c: 3, d: 4, e: { f: 5 } };

const clonedObj1 = clone(obj1);
const clonedObj2 = clone(obj2);

console.log(clonedObj1); // { a: 1, b: 2 }
console.log(clonedObj2); // { c: 3, d: 4, e: { f: 5 } }

// 修改原始对象
obj1.a = 10;
obj2.e.f = 20;

console.log(clonedObj1); // { a: 1, b: 2 }
console.log(clonedObj2); // { c: 3, d: 4, e: { f: 20 } }

const deepClone = obj => JSON.parse(JSON.stringify(obj));

示例：

const obj1 = { a: 1, b: 2 };
const obj2 = { c: 3, d: 4, e: { f: 5 } };

const clonedObj1 = deepClone(obj1);
const clonedObj2 = deepClone(obj2);

console.log(clonedObj1); // { a: 1, b: 2 }
console.log(clonedObj2); // { c: 3, d: 4, e: { f: 5 } }

// 修改原始对象
obj1.a = 10;
obj2.e.f = 20;

console.log(clonedObj1); // { a: 1, b: 2 }
console.log(clonedObj2); // { c: 3, d: 4, e: { f: 5 } }

const keys = obj => Object.keys(obj);

示例：

const obj1 = { a: 1, b: 2, c: 3 };
const obj2 = { name: 'John', age: 30, city: 'New York' };

console.log(keys(obj1)); // ['a', 'b', 'c']
console.log(keys(obj2)); // ['name', 'age', 'city']

const values = obj => Object.values(obj);

示例：

const obj1 = { a: 1, b: 2, c: 3 };
const obj2 = { name: 'John', age: 30, city: 'New York' };

console.log(values(obj1)); // [1, 2, 3]
console.log(values(obj2)); // ['John', 30, 'New York']

const entries = obj => Object.entries(obj);

示例：

const obj1 = { a: 1, b: 2, c: 3 };
const obj2 = { name: 'John', age: 30, city: 'New York' };

console.log(entries(obj1)); // [['a', 1], ['b', 2], ['c', 3]]
console.log(entries(obj2)); // [['name', 'John'], ['age', 30], ['city', 'New York']]

const fromEntries = arr => Object.fromEntries(arr);

示例：

const arr1 = [['a', 1], ['b', 2], ['c', 3]];
const arr2 = [['name', 'John'], ['age', 30], ['city', 'New York']];

console.log(fromEntries(arr1)); // { a: 1, b: 2, c: 3 }
console.log(fromEntries(arr2)); // { name: 'John', age: 30, city: 'New York' }

const isEmpty = obj => Object.keys(obj).length === 0;

示例：

const obj1 = { a: 1, b: 2 };
const obj2 = {};
const obj3 = { name: 'John' };

console.log(isEmpty(obj1)); // false
console.log(isEmpty(obj2)); // true
console.log(isEmpty(obj3)); // false

const renameKey = (obj, oldKey, newKey) => ({ …obj, [newKey]: obj[oldKey], [oldKey]: undefined });

示例：

const obj1 = { a: 1, b: 2 };
const obj2 = { name: 'John', age: 30 };

console.log(renameKey(obj1, 'a', 'x')); // { b: 2, x: 1, a: undefined }
console.log(renameKey(obj2, 'name', 'username')); // { age: 30, username: 'John', name: undefined }

const filterKeys = (obj, keys) => keys.reduce((o, k) => (obj.hasOwnProperty(k) ? { ...o, [k]: obj[k] } : o), {});

示例：

const obj1 = { a: 1, b: 2, c: 3, d: 4 };
const obj2 = { name: 'John', age: 30, city: 'New York' };

const filteredObj1 = filterKeys(obj1, ['a', 'c', 'e']);
const filteredObj2 = filterKeys(obj2, ['name', 'city', 'country']);

console.log(filteredObj1); // { a: 1, c: 3 }
console.log(filteredObj2); // { name: 'John', city: 'New York' }

const curry = fn => (…args) => args.length >= fn.length ? fn(…args) : curry(fn.bind(null, …args));

示例：

const add = (a, b, c) => a + b + c;
const curriedAdd = curry(add);

console.log(curriedAdd(1)(2)(3)); // 6
console.log(curriedAdd(1, 2)(3)); // 6
console.log(curriedAdd(1, 2, 3)); // 6

const memoize = fn => { const cache = {}; return (…args) => cache[args] = cache[args] || fn(…args); };

示例：

const fibonacci = (n) => {
  if (n < 2) return n;
  return fibonacci(n - 1) + fibonacci(n - 2);
};

const memoizedFibonacci = memoize(fibonacci);

console.log(memoizedFibonacci(10)); // 55
console.log(memoizedFibonacci(10)); // 55 (从缓存中取值)
console.log(memoizedFibonacci(20)); // 6765
console.log(memoizedFibonacci(20)); // 6765 (从缓存中取值)

const pipe = (…fns) => x => fns.reduce((v, f) => f(v), x);

示例：

const double = x => x * 2;
const addOne = x => x + 1;
const square = x => x * x;

const pipeline = pipe(double, addOne, square);

console.log(pipeline(2)); // 25

依次执行这些函数，从右到左，并将每个函数的输出作为下一个函数的输入。

const compose = (…fns) => x => fns.reduceRight((v, f) => f(v), x);

示例：

const double = x => x * 2;
const addOne = x => x + 1;
const square = x => x * x;

const composed = compose(square, addOne, double);

console.log(composed(2)); // 25 ==> 等价于 square(addOne(double(2)))
console.log(compose(5)); // 121 ==> 等价于 square(addOne(double(5)))
console.log(compose(10)); // 441 ==> 等价于 square(addOne(double(10)))

const throttle = (fn, wait) => {
    let lastTime = 0;
    return (…args) => {
        const now = new Date().getTime();
        if (now — lastTime >= wait) {
            lastTime = now; fn(…args);
        }
    };
};

示例：

const throttledFn = throttle((...args) => {
  console.log(...args);
}, 1000);

throttledFn('Hello'); // 输出 'Hello'
throttledFn('World'); // 不输出

setTimeout(() => {
  throttledFn('Hello'); // 输出 'Hello'
  throttledFn('World'); // 不输出
}, 1500);

setTimeout(() => {
  throttledFn('Hello'); // 输出 'Hello'
  throttledFn('World'); // 不输出
}, 2500);

const debounce = (fn, delay) => {
    let timeoutId;
    return (…args) => {
        clearTimeout(timeoutId);
        timeoutId = setTimeout(() => fn(…args), delay);
    };
};

示例：

const debounce = (fn, delay) => {
  let timeoutId;
  return (...args) => {
    clearTimeout(timeoutId);
    timeoutId = setTimeout(() => fn(...args), delay);
  };
};

const debouncedFn = debounce((...args) => {
  console.log(...args);
}, 500);

debouncedFn('Hello');
debouncedFn('World');

setTimeout(() => {
  debouncedFn('Hello');
}, 1000);

// 输出顺序为：
// "World"
// "Hello"

const once = fn => {
    let called = false;
    return (…args) => !called && (called = true, fn(…args));
};

示例：

const onceFn = once((...args) => {
  console.log(...args);
});

onceFn('Hello'); // 输出 'Hello'
onceFn('World'); // 不输出
onceFn('Hello1'); // 不输出

const reverse = str => str.split('').reverse().join('');

示例：

console.log(reverse('hello')); // olleh
console.log(reverse('abcdefg')); // gfedcba
console.log(reverse('')); // (空字符串)

const capitalize = str => str.charAt(0).toUpperCase() + str.slice(1).toLowerCase();

示例：

console.log(capitalize('hello')); // Hello
console.log(capitalize('world')); // World
console.log(capitalize('')); // (空字符串)

const isPalindrome = str => str === str.split('').reverse().join('');

示例：

console.log(isPalindrome('radar')); // true
console.log(isPalindrome('hello')); // false
console.log(isPalindrome('')); // true
console.log(isPalindrome('a')); // true

const repeat = (str, n) => str.repeat(n);

示例：

console.log(repeat('hello', 3)); // 'hellohellohello'
console.log(repeat('abc', 2)); // 'abcabc'
console.log(repeat('', 5)); // ''
console.log(repeat('a', 4)); // 'aaaa'

const countVowels = str => str.match(/[aeiou]/gi)?.length || 0;

示例：

console.log(countVowels('hello')); // 2
console.log(countVowels('world')); // 1
console.log(countVowels('')); // 0
console.log(countVowels('aeiou')); // 5

const trim = str => str.trim();

示例：

console.log(trim('   hello   ')); // 'hello'
console.log(trim('   world')); // 'world'
console.log(trim('hello   ')); // 'hello'
console.log(trim('')); // ''

const kebabCase = str => str.replace(/\s+/g, '-').toLowerCase();

示例：

console.log(kebabCase('hello world')); // 'hello-world'
console.log(kebabCase('Hello World')); // 'hello-world'
console.log(kebabCase('multiple   spaces')); // 'multiple-spaces'
console.log(kebabCase('')); // ''

const snakeCase = str => str.replace(/\s+/g, '_').toLowerCase();

示例：

console.log(snakeCase('hello world')); // 'hello_world'
console.log(snakeCase('Hello World')); // 'hello_world'
console.log(snakeCase('multiple   spaces')); // 'multiple_spaces'
console.log(snakeCase('')); // ''

const isEven = num => num % 2 === 0;

示例：

console.log(isEven(10)); // true
console.log(isEven(11)); // false
console.log(isEven(0)); // true
console.log(isEven(-10)); // true
console.log(isEven(-11)); // false

const isOdd = num => num % 2 !== 0;

示例：

console.log(isOdd(10)); // false
console.log(isOdd(11)); // true
console.log(isOdd(0)); // false
console.log(isOdd(-10)); // false
console.log(isOdd(-11)); // true

const random = (min, max) => Math.random() * (max — min) + min;

示例：

console.log(random(1, 10)); // 生成一个介于 1 和 10 之间的随机数
console.log(random(0, 100)); // 生成一个介于 0 和 100 之间的随机数
console.log(random(-10, 10)); // 生成一个介于 -10 和 10 之间的随机数

const randomInt = (min, max) => Math.floor(Math.random() * (max — min + 1)) + min;

示例：

console.log(randomInt(1, 10)); // 生成一个介于 1 和 10 之间的随机整数
console.log(randomInt(0, 100)); // 生成一个介于 0 和 100 之间的随机整数
console.log(randomInt(-10, 10)); // 生成一个介于 -10 和 10 之间的随机整数

const factorial = n => n <= 1 ? 1 : n * factorial(n — 1);

示例：

console.log(factorial(5)); // 120
console.log(factorial(3)); // 6
console.log(factorial(0)); // 1
console.log(factorial(1)); // 1

const fib = n => n <= 1 ? n : fib(n — 1) + fib(n — 2);

示例：

console.log(fib(10)); // 55
console.log(fib(5)); // 5
console.log(fib(0)); // 0
console.log(fib(1)); // 1

const gcd = (a, b) => b === 0 ? a : gcd(b, a % b);

示例：

console.log(gcd(48, 18)); // 6
console.log(gcd(101, 103)); // 1
console.log(gcd(12, 15)); // 3
console.log(gcd(24, 30)); // 6

const lcm = (a, b) => Math.abs(a * b) / gcd(a, b);

示例：

console.log(lcm(4, 6)); // 12
console.log(lcm(10, 15)); // 30
console.log(lcm(12, 18)); // 36
console.log(lcm(24, 30)); // 60

const toBinary = num => num.toString(2);

示例：

console.log(toBinary(10)); // '1010'
console.log(toBinary(20)); // '10100'
console.log(toBinary(30)); // '11110'
console.log(toBinary(40)); // '101000'

const toHex = num => num.toString(16);

示例：

console.log(toHex(10)); // 'a'
console.log(toHex(20)); // '14'
console.log(toHex(30)); // '1e'
console.log(toHex(40)); // '28'