> For the complete documentation index, see [llms.txt](https://lochiwei.gitbook.io/web/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://lochiwei.gitbook.io/web/js/val/obj/create/new.md).

# new

[JS](/web/js.md) ⟩ [value](/web/js/val.md) ⟩ [object](/web/js/val/obj.md) ⟩ [create](/web/js/val/obj/create.md) ⟩ new

{% hint style="success" %}
([operator](/web/js/grammar/op.md)) (:star2: [table of operators](/web/js/grammar/op/table-of-operators.md))

create objects by using [**constructor**](/web/js/val/func/constructor.md) functions.  (:point\_right: [callable vs. constructable](/web/js/val/obj/create/new/callable-vs.-constructable.md))

```javascript
new Object() 
new Point(2,3)

new Object        // empty pair of parentheses can be omitted
new Date
```

:u6307: <mark style="color:yellow;">**synonyms**</mark>： "<mark style="color:purple;">**object creation expression**</mark>"
{% endhint %}

{% tabs %}
{% tab title="🧨 雷區" %}
{% hint style="danger" %}
[**class**](/web/js/val/class.md) can <mark style="color:red;">**only**</mark>**&#x20;**<mark style="color:yellow;">**be instantiated**</mark> with the <mark style="color:purple;">**`new`**</mark> <mark style="color:yellow;">**operator**</mark> — attempting to call a class <mark style="color:red;">**without**</mark> <mark style="color:purple;">**`new`**</mark> will throw a [<mark style="color:red;">**`TypeError`**</mark>](/web/js/err/type.md):exclamation:
{% endhint %}
{% endtab %}

{% tab title="⭐️ 重點" %}
{% hint style="info" %} <mark style="color:yellow;">**objects**</mark> created by <mark style="color:purple;">**`new F()`**</mark> <mark style="color:yellow;">**use**</mark> [**`F.prototype`**](/web/js/val/func/prototype.md) <mark style="color:yellow;">**as**</mark> their [**prototype**](/web/js/val/obj/proto.md).
{% endhint %}

{% hint style="success" %}
a [**function**](/web/js/val/func.md) can know <mark style="color:yellow;">**whether it is invoked with**</mark> <mark style="color:purple;">**new**</mark> by <mark style="color:orange;">**checking**</mark> [**new.target**](/web/js/val/obj/create/new/new.target.md). [**new.target**](/web/js/val/obj/create/new/new.target.md) is <mark style="color:red;">**only**</mark> [**undefined**](/web/js/val/prim/undefined.md) <mark style="color:yellow;">**when**</mark> the function is <mark style="color:yellow;">**invoked**</mark> <mark style="color:red;">**without**</mark> <mark style="color:purple;">**new**</mark>.
{% endhint %}
{% endtab %}

{% tab title="👥 相關" %}

* [callable vs. constructable](/web/js/val/obj/create/new/callable-vs.-constructable.md)
* [new.target](/web/js/val/obj/create/new/new.target.md)
  {% endtab %}

{% tab title="📗 參考" %}

* [ ] [JavaScript: The Definitive Guide](/web/master/ref/javascript-the-definitive-guide.md) ⟩&#x20;
  * [x] 4.6 Object Creation Expressions
  * [ ] Ch. 9 Classes
    {% endtab %}

{% tab title="📘 手冊" %}

* [ ] [new](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/new)
  {% endtab %}
  {% endtabs %}


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