Edit in JSFiddle

$("#btn1").click(function(){
    //學生資料
    var Arr = [
        {name:"Chen",age:"20",country:"Taiwan"},
        {name:"Tom",age:"2１",country:"America"},
        {name:"Kotaro",age:"20",country:"Japan"},
        {name:"Wang",age:"19",country:"Taiwan"}
    ];
    
    //找出country為Taiwan的物件
    var newArr = $.grep(Arr,function(o,index){
        return (o.country == "Taiwan");
    });
    
    //組出學生姓名
    var s="";
    var comma="";
    $.each(newArr,function(i,o){
        s += comma + o.name;
        comma = ",";
    });
    
    alert(s);
});

<button id="btn1">show data</button>