星期五, 5月 20, 2011

[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

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