JS柯里化面试题

要求写一个方法 f,使得 +f(2, 3) // 5 +f(2)(3) // 6 +f(2, 3)(4) // 20 +f(2, 3)(4)(5) // 100 +f(1)(1)(1)(1, 1, 1) // 3 括号里为加，括号与括号间为乘

let array = [];
            let fun = function(...arg) {
                console.log(arg)
                if(arg != null){
                    let sum = arg.reduce((tmp, item, index)=>{
                        // console.log(tmp, item, index);
                        console.log(arg);
                        console.log(tmp + item);
                        array.push(tmp + item);
                    })
                    return fun;
                }else{
                    resultSum(array);
                }
            };
            
            let resultSum = function(arr){
                let num = 1;
                arr.forEach(item=>{
                    num *= item;
                })
                console.log(num);
                return num;
            }
            //sum([1,2,3,4])
            fun(1, 1, 1)(2, 3);