SOURCE

const isEmpty = function(obj){
    for(let newObj in obj){ 
        return false
    }
    return true
}

let sum = 0
const sumMoney = function(obj){
    for(let m in obj){
        sum += obj[m]
    }   
    return 0
}

let obj = {
}

console.log(isEmpty(obj))

let moneyObj = {
    zhangsan: 12000,
    lisi: 50000,
    wangwu: 90000
}

sumMoney(moneyObj)
console.log(sum)

const multiplyNumeric = function(obj){
    for(let i in obj){
        if(typeof obj[i] == 'number'){
            obj[i] *= 2
        }
    }
}

let obj2 = {
    num1: 22,
    num2: 44,
    st3: '所事事'
}
multiplyNumeric(obj2)
console.log(obj2)

let calculator = {
    read(n1,n2){
        this.num1 = ''?0:n1
        this.num2 = ''?0:n2
        console.log(calculator)
    },
    sum(){
        console.log(this.num1+this.num2)
    },
    mul(){
        console.log(this.num1*this.num2)
    }
}

calculator.read('1','')
calculator.sum()
calculator.mul()

let a = [1,2,3,4,5,6,7]
let b = []
console.log(a==b)
a.splice(2,2,20,50)
a.splice(-1,0,100,200,300)
console.log(a)