js 对象
删除属性
var xiaoming = { 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
检测对象是否有某一属性 用 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
要判断一个属性是否是xiaoming
自身拥有的,而不是继承得到的,可以用hasOwnProperty()
方法:
var xiaoming = { name: '小明' }; xiaoming.hasOwnProperty('name'); // true xiaoming.hasOwnProperty('toString'); // false