es5和es6中如何处理不确定参数

场景：求出不定参数的总数和

//利用arguments
function sum () {
   let num = 0
   //Array.prototype.forEach.call(arguments,function (item){
       //num += item * 1
   //})
   Array.from(arguments).forEach(function (item){
       num += item * 1
   })
   return num
}
//不用arguments
function sum (...nums) {
   let num = 0
   nums.forEach(function (item){
       num += item * 1
   })
   return num
}
console.log(sum(1,2,3,4,5))

场景：第一个参数*2再和剩余参数求和

function sum (base,...nums) {
   let num = 0
   nums.forEach(function (item){
       num += item * 1
   })
   return base * 2 +num
}
console.log(sum(1,2,3))