前端面试题 sum(1,2)(3).sumof 为 6

function sum(){
    let arr = [...arguments]
    let a = function(){
        let arg = [...arr,...arguments]
        return sum(...arg)
    }
    console.log(arr)
    a.sumof = function (){
        return arr.reduce((pre,cur)=>{
            return pre+cur
        },0)
    }
    return a
}