Cloning Non enumerable properties in javascript

Question

I have all non - enumerable properties in object, I want to clone that object.

My problem non-enumerable properties are not getting cloned.

Take below example

 Object.defineProperty(this, 'prop', {
        get: function () {
            return prop;
        },
        set: function (value) {
            prop= value;
        }
    });

   Object.defineProperty(this, 'newprop', {
        get: function () {
            return newprop;
        },
        set: function (value) {
            newprop= value;
        }
    });

For example I have above two properties in my object doing clone using following methods, my properties are not getting cloned I believe it is because they are non - enumerable.

   var newObject = $.extend({},oldObject);
   var newObject= Object.assign({},oldobject);

How do I copy non-enumerable properties in javascript.

Answer 1

If one or more properties aren't enumerable, how do you want to auto-magically enumerate them?

Since you know their names, you should do something like this:

var sourceObj = this;
var targetObj = {};

["prop", "otherProperty"].forEach(function(property) {
    targetObj[property] = sourceObj[property]; 
});

Or you can build the whole property name array whenever you define a non-enumerable property:

   var propertyNames = [];

   Object.defineProperty(this, 'newprop', {
        get: function () {
            return newprop;
        },
        set: function (value) {
            newprop= value;
        }
    });
    propertyNames.push("newprop"); // <---


   Object.defineProperty(this, 'newprop2', {
        get: function () {
            return newprop;
        },
        set: function (value) {
            newprop= value;
        }
    });
    propertyNames.push("newprop2"); // <---

propertyNames.forEach(function(property) {
    targetObj[property] = sourceObj[property]; 
});

Alternate approach: Object.getOwnPropertyNames

The Object.getOwnPropertyNames() method returns an array of all properties (enumerable or not) found directly upon a given object.

Maybe this is the best approach. Object.getOwnPropertyNames gets the name of own object's properties either if they're enumerable or not. That is, you can avoid building the whole propertyNames array, and this approach should be fine with you because you said that all properties aren't enumerable:

var sourceObj = this;
var targetObj = {};    

Object.getOwnPropertyNames(sourceObj).forEach(function(property) {
    targetObj[property] = sourceObj[property]; 
});

Answer 2

您可以使用 Object.defineProperties 和 Object.getOwnPropertyDescriptors() 函数

<块引用>

Object.defineProperties() 方法直接在对象上定义新属性或修改现有属性，返回该对象。

<块引用>

Object.getOwnPropertyDescriptors() 方法返回给定对象的所有属性描述符。

所以，您可以将原始对象的属性添加到一个空对象中，如下

var source_obj = this
var cloned_obj = Object.defineProperties({}, Object.getOwnPropertyDescriptors(source_obj));

Answer 3

我在How to implement Ruby's extend module in JavaScript中有类似的问题。

因为我不想使用迭代将每种方法附加到新对象上，所以我能做的最好的方法就是这样，欢迎给我任何想法和建议，谢谢。

class Test {

  constructor(name) {

    this.name = name;
  }

  test1(){
    return this.name + "test1"
  }
}

const Other = {
  test2: function(){
    return this.name + "test2"
  },

  test3: function(){
    return this.name + "test3"
  },

  test4: function(){
    return this.name + "test4"
  }

}

var person = new Test("HKE")
Object.assign(person,Other) //this like object.extend(Module) in ruby
console.log(person.test1()) // HKEtest1
console.log(person.test2()) // HKEtest2
console.log(person.test3()) // HKEtest3
console.log(person.test4()) // HKEtest4

var house = new Test("Tsao")
console.log(house.test1())
console.log(house.test2()) // TypeError: house.test2 is not a function
console.log(house.test3()) // TypeError: house.test3 is not a function
console.log(house.test4()) // TypeError: house.test4 is not a function