澄清Javascript Object.defineProperties的用法

本文介绍了澄清Javascript Object.defineProperties的用法的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我仍然不觉得我完全理解Object.defineProperties的使用，所以我很欣赏以下（有点人为的）例子的一些输入：

I still don't feel like I completely understand the use of Object.defineProperties, so I'd appreciate some input on the following (somewhat contrived) examples:

var Class_1 = function (arg) {
    this.my_val = arg;
};

var Class_2 = function (arg) {
    Object.defineProperties(this,{
        my_val : {
            value : arg,
            writable : true,
            enumerable : true,
            configurable : true
        }
    });
};

var one = new Class_1("foo");
var two = new Class_2("foo");

以及仅使用 defineProperties 的原因在Class_1中分配它就像你想要可写，可枚举或可配置是假的;基本上它是为了控制。否则简单的 this.property 定义是相同的，对吗？

And the reasoning for using defineProperties over just assigning it like in Class_1 would be when you want writable, enumerable or configurable to be false; Basically it's for control. Otherwise the simple this.property definition is identical, correct?

var Class_value = function (arg) {
    Object.defineProperties(this, {
        my_val : {
            value : arg, 
            writable : true,
//          enumerable : false   // default
//          configurable : false // default
        }
    });
};

var Class_getSet = function (arg) {
    Object.defineProperties(this, {
        __my_val : {
            value : arg,
            writable : true,
//          enumerable : false   // default
//          configurable : false // default
        },
        my_val : {
            get : function(){ return this.__my_val; }, 
            set : function(new_val){ this.__my_val = new_val; }
        }
    });
};

var three = new Class_value("foo");
var four = new Class_getSet("foo");

使用获取 / 设置函数只需值就可以添加更多高级逻辑，例如在<$ c $时调用另一个函数c> my_val 已更新，或发送事件等。此外，您无法使用获取 / 设置至少没有定义初始值（通过此处显示的值属性，或通过简单的 this.property = ... 定义如 1。），对吗？

And the reasoning for using get/set functions over just value would be when you want to add more advanced logic, like calling another function when my_val is updated, or sending an event, etc. Also you cannot use get/set without at least defining the initial value (either via a value property shown here, or via the simple this.property = ... definition as in 1.), correct?

基本上我我只是想确保我理解如何以及何时使用defineProperties的原因，因为我觉得我还没有很好地处理这个概念。

Basically I'm just looking to make sure that I understand the reasoning for how and when to use defineProperties, since I feel like I don't have a good handle on the concept yet.

defineProperties

澄清Javascript Object.defineProperties的用法

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