JavaScript : 找出物件的所有屬性

//找出物件的所有屬性
function listPropertyName(obj){
var names = "";
for(var names in obj)
names += names + "\n";
alert(names);
}

//取得股票總值
var value = 0;
for (stock in portfolio){
value += get_share_value(stock) * portfolio[stock];
}

for(var i = 0; i < fruits.length; i++)
if (fruits[i]) alert(fruits[i]);