Javascript Number與Jquery.Number

var test1= "1234.5678";
var number=Number(test1);//new Number(1234.5678);
number.toFixed(2);//1234.56

//需要引用 jQuery Number Format 插件
var test2=$.Number(1234.5678,2);//1234.56
var test3=$.Number(1234.5678);   //1234