1. 设置 configurable: false; writable: false 后，属性会不可删除不可修改，但可以新增属性

**2. Object.**preventExtensions() 可以让对象不可新增属性

var obj = {a: 2};
Object.preventExtensions(obj)
obj.b = 3;
console.log(obj);

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Object.isExtensible() 是否可拓展

var obj = {a: 2};
var obj2 = {a: 2};
Object.preventExtensions(obj)
console.log(Object.isExtensible(obj));
console.log(Object.isExtensible(obj2));

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使用 Object.defineProperty() 添加的属性，属性描述符默认是 false

var obj = {a: 2};
obj.c = 8;
Object.defineProperty(obj, 'b', {
	value: 6
})
console.log(Object.getOwnPropertyDescriptor(obj, 'b'));
console.log(Object.getOwnPropertyDescriptor(obj, 'c'));

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3. Object.seal() 使对象密封, Object.isSealed() 对象是否密封

var obj = {a: 2};
Object.seal(obj);
obj.b = 3;
console.log(Object.isSealed(obj));
console.log(obj);

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4. Object.freeze() 冻结对象

var obj = {a: 2};
Object.freeze(obj);
console.log(Object.isFrozen(obj));

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⭐️ 封装深层冻结对象

function myFreeze(obj) {
	Object.freeze(obj);
  for (var key in obj) {
  	if (typeof(obj[key]) === 'object' && obj[key] !== null) {
    	myFreeze(obj[key]);
    }
  }
}

var obj = {
	a: {
  	b: {
    	c: 123
    }
  }
}

myFreeze(obj);

obj.a.b.d = 345;

console.log(obj);

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is 比较运算的扩充