ES6-- rest参数

（...x）Rest 参数接受函数的多余参数，组成一个数组

function sum(x, y, m) {
                let total = 0;
                if (x) total += x;
                if (y) total += y;
                if (m) total += m;
                console.log(`total:${total}`)  //11
            }
            sum(5, 6)
            let sum1 = (...x)=>{  //
                let total=0;
                for(var i of x)
                {
                     total+=i;
                }
                console.log(`total:${total}`)
            }
           sum1(7,8,9)  //24