...theArgs剩余参数

 

1. 当在JS方法中我们不能确定参数数量的情况时 用来表示这些参数：
   

   function sum(...theArgs) {
            return theArgs.reduce((previous,current) => {
                return previous + current
            }
       );
   }
   console.log(sum(1,2,3));
   //expected output:6
   console.log(sum(3,3,3,3));
   //expected output:12
   

2. ...theArgs是一个真正的Array实例 -> 你可以在上面直接使用所有的数组方法:
   

   function checkRule(...theArgs){
            var sorted = theArgs.sort();
            return sorted;
   }
   console.log(checkRule(1,5,2,7));
   //expected output:[1,2,5,7]