new Set()去重、判断对象、判断空数组

1. 数字

const numbers = [2, 3, 4, 4, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 5, 32, 3, 4, 5]
console.log([...new Set(numbers)]); // [2, 3, 4, 5, 6, 7, 32]

2. 字符串

const str = ['123', '12', '123', '12', 1, '1', 'a']
console.log([...new Set(str)]); // [ '123', '12', 1, '1', 'a' ]

3. 对象(这种情况下，new Set()里面需要接的是strings类型)

const list = [{
        name: "张三",
        age: 18,
        address: "北京"
    },
    {
        name: "李四",
        age: 20,
        address: "天津"
    },
    {
        name: "张三",
        age: 18,
        address: "北京"
    },
]
let newList = list.map(item => {
    return JSON.stringify(item)
})

let res = Array.from(new Set(newList)).map((item) => JSON.parse(item))
console.log(res);
// [
//     { name: '张三', age: 18, address: '北京' },
//     { name: '李四', age: 20, address: '天津' }
// ]

3. 数组，(这种情况下，new Set()里面需要接的是strings类型)

let arr = [
    [1],
    [2],
    [1, [1, [2]]],
    [1, [1, [2]]],
    [1, [1, 2]],
    [1, [1, 2]],
    [2]
]
let newArr = arr.map(item => {
    return JSON.stringify(item)
})
let res = Array.from(new Set(newArr)).map((item) => JSON.parse(item))
console.log(res);
// [
//     [1],
//     [2],
//     [1, [1, [1, [2]]]],
//     [1, [1, 2]]
// ]

4.判断对象

• val != null && val.constructor == Object

let arr = [], obj = {}
console.log(obj != null && obj.constructor == Object); // true
console.log(arr != null && arr.constructor == Object); // false

• Object.prototype.toString.call(val) == '[object Object]'

// Object.prototype.toString.call(val) == '[object Object]'
console.log(Object.prototype.toString.call(obj) == '[object Object]'); //true
console.log(Object.prototype.toString.call(arr) == '[object Object]'); //false

5.判断空数组

const isNotEmpty = (arr) => Array.isArray(arr) && Object.keys(arr).length > 0;
const isNotEmpty = (arr) => JSON.stringify(arr) === '{}';

6.判断空对象

const isEmpty = (obj) => JSON.stringify(obj) === '{}';