name: '小明',
birth: 1990,
school: 'No.1 Middle School',
height: 1.70,
weight: 65,
score: null
};
name: '小红',
'middle-school': 'No.1 Middle School'
};
xiaohong的属性名middle-school不是一个有效的变量,就需要用''括起来。访问这个属性也无法使用.操作符,必须用['xxx']来访问:
xiaohong['name']; // '小红'
xiaohong.name; // '小红'
实际上javascript对象的所有属性都是字符串,不过属性对应的值可以是任意的数据类型。
name: '小明'
};
xiaoming.age; // undefined
name: '小明'
};
xiaoming.age; // undefined
xiaoming.age = 18; // 新增一个age属性
xiaoming.age; // 18
delete xiaoming.age; // 删除age属性
xiaoming.age; // undefined
delete xiaoming['name']; // 删除name属性
xiaoming.name; // undefined
delete xiaoming.school; // 删除一个不存在的school属性也不会报错
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
不过要小心,如果in判断一个属性存在,这个属性不一定是xiaoming的,它可能是xiaoming继承得到的:
运行代码:
name : '小明',
age : 18,
'your-school' : 'No.1 Middle School',
height : 1.78,
weight : 65
};
document.write(xiaoming.name + '<br>');//访问对象属性
document.write(xiaoming['your-school'] + '<br>');//访问含有特殊字符的属性名
document.write(xiaoming['height'] + '<br>');
xiaoming.name = '改名字啦';//动态改变属性
document.write('删除属性开始<br>');
document.write(xiaoming.friends + '<br>');//访问不存在的属性,返回undefined
delete xiaoming.name;//删除对象属性
for(x in xiaoming){
document.write(xiaoming[x] + '<br>');
}
if('weight' in xiaoming){//检查xiaoming是否拥有weight这个属性
document.write('weight属于对象xiaoming的属性<br>');
}
if('toString' in xiaoming){//检查xiaoming是否拥有toString这个属性,toString定义在对象中
document.write('toString属于对象xiaoming的属性<br>');
}
if(xiaoming.hasOwnProperty('toString')){//检查xiaoming是否拥有toString这个属性
document.write('toString属于对象xiaoming的属性<br>');
}else{
document.write('toString不属于对象xiaoming的属性<br>');
}
运行结果: