var xiaoming = {
    name: '小明',
    birth: 1990,
    school: 'No.1 Middle School',
    height: 1.70,
    weight: 65,
    score: null
};

注意最后一個(gè)鍵值沒(méi)有,

xiaoming.name; // '小明'
xiaoming.birth; // 1990

屬性名包含特殊字符

只能使用['xxx']來(lái)訪問(wèn)

var xiaohong = {
    name: '小紅',
    'middle-school': 'No.1 Middle School'
};

xiaohong['middle-school']; // 'No.1 Middle School'
xiaohong['name']; // '小紅'
xiaohong.name; // '小紅'

訪問(wèn)不存在的屬性返回undefined

var xiaoming = {
    name: '小明'
};
xiaoming.age; // undefined

JavaScript的對(duì)象是動(dòng)態(tài)類(lèi)型

自由地給一個(gè)對(duì)象添加或刪除屬性

var xiaoming = {
    name: '小明'
};
xiaoming.age; // undefined
xiaoming.age = 18; // 新增一個(gè)age屬性
xiaoming.age; // 18
delete xiaoming.age; // 刪除age屬性
xiaoming.age; // undefined
delete xiaoming['name']; // 刪除name屬性
xiaoming.name; // undefined
delete xiaoming.school; // 刪除一個(gè)不存在的school屬性也不會(huì)報(bào)錯(cuò)

檢測(cè)對(duì)象是否擁有某一屬性

in

var xiaoming = {
    name: '小明',
    birth: 1990,
    school: 'No.1 Middle School',
    height: 1.70,
    weight: 65,
    score: null
};
'name' in xiaoming; // true
'grade' in xiaoming; // false

'toString' in xiaoming; // true 繼承的

判斷屬性是自身?yè)碛械?，還是繼承得到的

var xiaoming = {
    name: '小明'
};
xiaoming.hasOwnProperty('name'); // true
xiaoming.hasOwnProperty('toString'); // false