es6可变参数-扩展运算符

//求参数和
function f(){
  var a = Array.prototype.slice.call(arguments);
  var sum = 0;
  a.forEach(function(item){
     sum += item*1;          
  })     
  return sum;  
};
f(1,2,3);//6

function f(...a){
  let sum = 0;
  a.forEach(item =>{
     sum += item*1;
  })    
  return sum;  
}
f(1,2,3);//6

//es5
var param = [‘hello‘,true,7];
var other = [1,2].concat(param);
console.log(other);//[1, 2, "hello", true, 7]

//es6
var param = [‘hello‘,true,7];
var other = [1,2,...param];
console.log(other);// [1, 2, "hello", true, 7]