【JavaScript】對象 obj.name 語法與 obj[name]語法

obj.name ==> obj["name"]  底層的自動轉化,所以直接寫 obj["name"] 效率會高一些

var obj = {
    name: "zhangsan",
    age: 12,
    sex: "male"            
}

console.log(obj.name); // "zhangsan"
console.log(obj["name"]); // "zhangsan"
console.log(obj[name]); // 會報錯: name is not defined

常見錯誤: 變量字符串化

var obj = {
    name: "zhangsan",
    age: 12,
    sex: "male"
}
for (var prop in obj) {
    console.log(obj.prop); // undefined * 3  : prop不再是變量 轉化為obj["prop"]
}