# internal property

[JS](https://lochiwei.gitbook.io/web/js) ⟩ [value](https://lochiwei.gitbook.io/web/js/val) ⟩ [object](https://lochiwei.gitbook.io/web/js/val/obj) ⟩ [property](https://lochiwei.gitbook.io/web/js/val/obj/prop) ⟩ internal property

{% hint style="success" %}
for <mark style="color:yellow;">**most operations**</mark> on [**objects**](https://lochiwei.gitbook.io/web/js/val/obj), there’s an “<mark style="color:purple;">**internal method**</mark>” in the [**JS spec**](https://lochiwei.gitbook.io/web/master/ref/js-spec) that describes how it works at the lowest level. For instance:

* <mark style="color:purple;">\[\[Get]]</mark> `-` internal method to **read** a property
* <mark style="color:purple;">\[\[Set]]</mark> `-` internal method to **write** a property

:warning: these methods are <mark style="color:red;">**only**</mark>**&#x20;**<mark style="color:yellow;">**used in the spec**</mark>, we <mark style="color:red;">**can’t call them directly**</mark>:exclamation:
{% endhint %}

{% tabs %}
{% tab title="⭐️ 重點" %}
{% hint style="warning" %}

* ( not:question:) every [func](https://lochiwei.gitbook.io/web/js/val/func "mention") <mark style="color:yellow;">**supports**</mark> the [\[\[Call\]\]](https://tc39.es/ecma262/#table-additional-essential-internal-methods-of-function-objects) <mark style="color:purple;">**internal method**</mark>.
* every [constructor](https://lochiwei.gitbook.io/web/js/val/func/constructor "mention") <mark style="color:yellow;">**supports**</mark> the [\[\[Construct\]\]](https://tc39.es/ecma262/#table-additional-essential-internal-methods-of-function-objects) <mark style="color:purple;">**internal method**</mark>.&#x20;

:point\_right: [callable-vs.-constructable](https://lochiwei.gitbook.io/web/js/val/obj/create/new/callable-vs.-constructable "mention")
{% endhint %}
{% endtab %}

{% tab title="🔴 主題" %}

* :scales: [callable-vs.-constructable](https://lochiwei.gitbook.io/web/js/val/obj/create/new/callable-vs.-constructable "mention")
* [environment](https://lochiwei.gitbook.io/web/js/concept/execution-context/lexical-environment/environment "mention") - lexical environment where a function was made.
* [home-object](https://lochiwei.gitbook.io/web/js/val/obj/method/home-object "mention")
  {% endtab %}

{% tab title="👥 相關" %}

* [proxy](https://lochiwei.gitbook.io/web/js/val/builtin/proxy "mention")
* [mixin](https://lochiwei.gitbook.io/web/js/val/obj/extend/mixin "mention") uses internal methods to [get/set](https://lochiwei.gitbook.io/web/js/val/class/member/getter-setter) properties.
  {% endtab %}

{% tab title="📗 參考" %}

* [ ] JS.info ⟩ [Proxy and Reflect](https://javascript.info/proxy)
  {% endtab %}
  {% endtabs %}


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