详解javascript对象的数据属性与访问器属性

var person = new Object();
person.name = 'Nicy';
person.age = 21;
person.sayName = function() {
    console.log(this.name);
};        
var person = {
    name: 'Nicy',
    age: 21,
    sayName: function() {
        console.log(this.name);
    }
}

var person = {}；

Object.defineProperty(person, "name", {
    value: 'Nicy'
})
person.name = 'Lee';　　
console.log(person.name)    // 'Nicy'

Object.defineProperty(person, "name", {
    writable: true
})
person.name = 'Lee';
console.log(person.name)    // 'Lee'

<span style="font-size: 13px;"><span style="color: #0000ff;"></span>var person = {<br/>    name: 'Nicy',<br/>    age: 21,<br/>    sayName: function() {<br/>        console.log(this.name);<br/>    }<br/>}<br/><br/>Object.defineProperty(person, "name", {<br/>    configurable: false<br/>})<br/><br/>delete person.name;    // 操作被忽略，无法通过delete删除属性<br/>Object.defineProperty(person, "name", {    // throw error<br/>    configurable:true    <br/>})     <br/>Object.defineProperty(person, "name", {    // throw error<br/>    enumerable: false<br/>})  <br/>Object.defineProperty(person, "name", {     // 由于writable为true，所以可以修改value<br/>    value: 'Lucy'<br/>})console.log(person.name)    // Lucy<br/>Object.defineProperty(person, "name", {    // writable可进行true -> false的单向修改<br/>    writable: false<br/>})<br/>Object.defineProperty(person, "name", {     // throw error<br/>    value: 'Lee'<br/>})<br/>Object.defineProperty(person, "name", {    // throw error，此时writable不可以false -> true<br/>    writable: true<br/>})<span style="color: #000000;"></span></span>

var person = {};
Object.defineProperty(person, "a", { value : 1, enumerable:true });
Object.defineProperty(person, "b", { value : 2, enumerable:false });
Object.defineProperty(person, "c", { value : 3 }); // enumerable defaults to false
person.d = 4; // 如果使用直接赋值的方式创建对象的属性，则这个属性的enumerable默认为true

for (var i in person) {    
  console.log(i);  
}　　//  'a' 和 'd' 

Object.keys(person); // ["a", "d"]

var person = {
    name: 'Nicy',
    _age: 21,
    year: 1997,
    _year: 1997,
    sayName: function() {
        console.log(this.name);
    }
}

Object.defineProperty(person, "age", {
    get: function() {
        return this._age;
    },
    set: function(value) {
        this._age = value;
                // ...
    }
})

// 设置get和set其中任意一个即可转换为访问器属性
Object.defineProperty(person, "year", {
    get: function() {
//        return this,year;    // error
        return this._year;    
    },
    set: function(value) {
//             this.year = value;　　// error
        this._year= value;
    }
})

var descriptor = Object.getOwnPropertyDescriptor(person, 'year');
console.log(descriptor);    // {get: ƒ, set: ƒ, enumerable: true, configurable: true}

Object.defineProperty(person, "job", {
    configurable: true,
    enumerable: true,
    get: function() {
        return this._job;
    },
    set: function(value) {
        this._job = value;
    }
})

// 设置value和writable其中任意一个即可转换为数据属性        
Object.defineProperty(person, "job", {
    value: 'worker',
    writable: true
})

var descriptor = Object.getOwnPropertyDescriptor(person, 'job');
console.log(descriptor);    // {value: "worker", writable: true, enumerable: true, configurable: true}

var person = {};
Object.defineProperties(person, {
  name: {
    value: 'Nicy',
    writable: true
  },
  _age: {
    value: 21,
    enumerable: true,
    writable: true,
    configurable: true
  },
   age: {
    get: function() {
    return this._age;
    },
    set: function(value) {
    this._age = value;
    }
  }
});