JavaScript 巧学巧用

let arr = [1, 2, 2, 3];
let set = new Set(arr);
let newArr = Array.from(set); // Array.from方法可以将 Set 结构转为数组。

console.log(newArr); // [1, 2, 3]

let obj1 = {a: 1};
let obj2 = {b: 2};
let obj3 = Object.assign({}, obj1, obj2);

console.log(obj3); // {a: 1, b: 2}

let arr3 = [1, 2, 3, 4, 5];
let newArr3 = arr3.map((e, i) => e * 10); // 给数组每一项乘以10
console.log(newArr3); // [10, 20, 30, 40, 50]

let arr4 = [1, 2, 3, 4, 5];
let newArr4 = arr4.filter((e, i) => e % 2 === 0); // 取模，过滤余数不为0的数
console.log(newArr4); // [2，4]

let arr5 = [{result: true}, {result: false}];

let newArr5 = arr5.some((e, i) => e.result); // 只要一个为true，即为true

console.log(newArr5); // true

let arr6 = [{result: true}, {result: false}];

let newArr6 = arr6.every((e, i) => e.result); // 只要一个为false，即为false

console.log(newArr6); // false

let a = 1.23;
let b = -1.23;

console.log(~~a); // 1
console.log(~~b); // -1

let c = 1;
let d = c || 2; // 如果c的值为true则取存在的值，否则为2

console.log(d); // 1

let [num1, ...nums] = [1, 2, 3];

console.log(num1); // 1
console.log(nums); // [2, 3]

let e = true,
  f = '';

if (e) {
  f = 'man';
} else {
  f = 'woman';
}

// 等同于
e ? f = 'man' : f = 'woman';