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js中一些便捷用法

1. 交换两个变量而无需临时变量

let a = 5, b = 10;[a, b] = [b, a];
console.log(a, b); // 10, 5

2、 检查数字是否为偶数

const isEven = num => num % 2 === 0;
console.log(isEven(8)); // trueconsole.log(isEven(7)); // false

3、从数组中删除重复项

const unique = arr => [...new Set(arr)];
console.log(unique([1, 2, 2, 3, 3, 4])); // [1, 2, 3, 4]

4、展平数组（一层）

const flat = arr => arr.flat();
console.log(flat([[1, 2], [3, 4]])); // [1, 2, 3, 4]

5、对数组中的所有数字求和

const sum = arr => arr.reduce((a, b) => a + b, 0);
console.log(sum([1, 2, 3, 4])); // 10

6、反转字符串

const reverse = str => str.split('').reverse().join('');
console.log(reverse("hello")); // "olleh"

7、检查字符串是否为回文

const isPalindrome = str => str === str.split('').reverse().join('');
console.log(isPalindrome("radar")); // true
console.log(isPalindrome("hello")); // false

8、将字符串的首字母大写

const capitalize = str => str.charAt(0).toUpperCase() + str.slice(1);
console.log(capitalize("javascript")); // "Javascript"

9、获取数组中的最大值

const max = arr => Math.max(...arr);
console.log(max([3, 8, 1, 5])); // 8

10、获取数组中的最小值

const min = arr => Math.min(...arr);
console.log(min([3, 8, 1, 5])); // 1

11、生成数字数组

const range = n => [...Array(n).keys()];
console.log(range(5)); // [0, 1, 2, 3, 4]

12、检查数组是否为空

const isEmpty = arr => arr.length === 0;
console.log(isEmpty([])); // trueconsole.log(isEmpty([1, 2])); // false

13、 克隆数组

const clone = arr => [...arr];
const arr = [1, 2, 3];
const copy = clone(arr);
copy.push(4);
console.log(arr, copy); // [1, 2, 3], [1, 2, 3, 4]

14、将数组转换为对象

const toObject = arr => Object.fromEntries(arr);
console.log(toObject([["name", "Alice"], ["age", 25]])); // { name: "Alice", age: 25 }

15、合并两个数组

const merge = (arr1, arr2) => [...new Set([...arr1, ...arr2])];
console.log(merge([1, 2], [2, 3])); // [1, 2, 3