JavaScript的Object.defineProperty详解

// 示例1
var obj = {};

// 直接使用=赋值
obj.a = 1;

// 使用Object.defineProperty定义
Object.defineProperty(obj, "b",
{
 value: 2
});

console.log(obj) // 打印"{a: 1, b: 2}"

// 示例2
var obj = {};

obj.a = 1;

Object.defineProperty(obj, "b",
{
 value: 2
});

console.log(Object.getOwnPropertyDescriptor(obj, "a")); // 打印"{value: 1, writable: true, enumerable: true, configurable: true}"
console.log(Object.getOwnPropertyDescriptor(obj, "b")); // 打印"{value: 2, writable: false, enumerable: false, configurable: false}"

// 示例3
var obj = {};

obj.name = "Fundebug";
console.log(Object.getOwnPropertyDescriptor(obj, "name")); // 打印{value: "Fundebug", writable: true, enumerable: true, configurable: true}

// 示例4
var obj = {};

Object.defineProperty(obj, "name",
{
 value: "Fundebug",
 writable: true,
 enumerable: true,
 configurable: true
});
console.log(Object.getOwnPropertyDescriptor(obj, "name")); // 打印{value: "Fundebug", writable: true, enumerable: true, configurable: true}

// 示例5
var obj = {};

Object.defineProperty(obj, "name",
{
 value: "Fundebug"
});
console.log(Object.getOwnPropertyDescriptor(obj, "name")); // 打印{value: "Fundebug", writable: false, enumerable: false, configurable: false}

// 示例6
var obj = {};

Object.defineProperty(obj, "name",
{
 value: "Fundebug",
 writable: false,
 enumerable: false,
 configurable: false
});
console.log(Object.getOwnPropertyDescriptor(obj, "name")); // 打印{value: "Fundebug", writable: false, enumerable: false, configurable: false}

// 示例7
var obj = {};

Object.defineProperty(obj, "name",
{
 value: "Fundebug"
});

// writable为false，无法赋值
obj.name = "云麒";
console.log(obj.name); // 打印"Fundebug"

// enumerable为false，无法遍历
console.log(Object.keys(obj)); // 打印"[]"

// configurable为false，无法删除
delete obj.name;
console.log(obj.name); // 打印"Fundebug"

// 示例8
"use strict"

var obj = {};

Object.defineProperty(obj, "name",
{
 value: "Fundebug",
 writable: false,
 enumerable: true,
 configurable: true
});

obj.name = "云麒"; // 报错“Uncaught TypeError: Cannot assign to read only property 'name' of object '#<Object>'”

// 示例9
"use strict"

var obj = {};

Object.defineProperty(obj, "name",
{
 value: "Fundebug",
 writable: true,
 enumerable: false,
 configurable: true
});

console.log(Object.keys(obj)) // 打印"[]"

// 示例10
"use strict"

var obj = {};

Object.defineProperty(obj, "name",
{
  value: "Fundebug",
  writable: true,
  enumerable: true,
  configurable: false
});

delete obj.name // 报错“Uncaught TypeError: Cannot delete property 'name' of #<Object>”

// 示例11
"use strict"

var obj = {};

Object.defineProperty(obj, "name",
{
  value: "Fundebug",
  writable: false,
  configurable: false
})

Object.defineProperty(obj, "name",
{
  value: "云麒"
}) // 报错“Uncaught TypeError: Cannot redefine property: name”