[書]JavaScript: 優良部份

擷取

• 企圖擷取不存在的屬性，會產生undefined
  stooge['middle-name'] //undefined
flight.status //undefined
  

  較好的做法 - 給予預設值
  var middle = stooge['middle-name'] || "(none)";
var status = flight.status || "unknown";

• 企圖從undefined取值，將丟出TypeError
  可利用&&防衛此狀況
  flight.equipment //undefined
flight.equipment.model //丟出"TypeError"
flight.equipment && flight.equipment.model //undefined


減少全域變數
全域變教會削弱程式的彈性，利用物件包裝
var MYAPP = { };
//利用這個變數保存全域變數
MYAPP.flight = {
airline: "Oceanic",
number:815
};



Reference

JavaScript: The Good Parts - 中譯:JavaScript: 優良部份