JavaScript Object需要注意的二三事

• 取值
  用object.prop方式取值

var company = {
    name: 'google',
    age: '28',
    money: 'I do not known'
}
company.name            //'google'

• 用object['propname']
  当属性名不是一个有效的变量名时，只能使用这种方法获取

var company = {
    name: 'google',
    age: '28',
    money: 'I do not known',
    'my-job': 'coding'
}
company['my-job']       // 'coding'

注意：定义一个Object时，属性名尽量为有效的变量名，这样便于取值

• 可以自由的添加删除对象的属性

var jake = {
    name: '小明'
};
jake.age; // undefined
jake.age = 18; // 新增一个age属性
jake.age; // 18
delete jake.age; // 删除age属性
jake.age; // undefined
delete jake['name']; // 删除name属性
jake.name; // undefined
delete jake.school; // 删除一个不存在的school属性也不会报错

判断Object的某个属性是否存在

• in

var company = {
    name: 'google',
    age: '28',
    money: 'I do not known'
}
'name' in company       // true
'age' in company       // true

• hasOwnProperty

var company = {...}
'name' in company       // true
'toString' in company   // true 

in虽然能判断属性是否存在，但是对象继承的属性也会参与判断，就导致上面这种情况，这时就需要使用hasOwnProperty

var company = {...}
company.hasOwnProperty('name')       // true
company.hasOwnProperty('toString')   // false