test(5);

 test(5,5);

 function test(a){

     alert(a);

 }

 function test(a,b){

     alert(a+b);

 }

  function sayHi() {

     if (arguments.length==1) {

         alert(arguments[0] + "你好，我是第一个sayHi方法！");

     } else if (arguments.length == 2) {

         alert(arguments[0] + "," + arguments[1] + "你好，我是第二个sayHi方法！");

     } else if (arguments.length == 3) {

         alert(arguments[0] + "," + arguments[1]+","+arguments[2] + "你好，我是第三个sayHi方法！");

     }

 }

 sayHi();//没有进入函数

 sayHi("Tom");

 sayHi("Tom", "lucy");

 sayHi("Tom","lucy","jame");