# type

[JS](/web/js.md) ⟩ [value](/web/js/val.md) ⟩ type

{% hint style="warning" %}
🚧
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{% tabs %}
{% tab title="⭐️ 重點" %}
{% hint style="warning" %}
there is <mark style="color:red;">**no**</mark> <mark style="color:purple;">**type**</mark> <mark style="color:yellow;">**associated**</mark> with [variable declaration](/web/js/variable/declare.md):exclamation:
{% endhint %}

{% hint style="info" %}
The <mark style="color:yellow;">**operands**</mark> of [comparison operator](/web/js/grammar/op/relational/compare.md) may be <mark style="color:yellow;">**of**</mark>**&#x20;**<mark style="color:red;">**any**</mark> <mark style="color:purple;">**type**</mark>.
{% endhint %}
{% endtab %}

{% tab title="🔴 主題" %}

* <mark style="color:yellow;">**main topics**</mark>
  * [type name](/web/js/val/type/name.md)
  * [custom type name](/web/js/val/type/name/custom-type-name.md)
  * [Broken mention](broken://pages/l1v0bwCArjuB3OOG3NfE)
* <mark style="color:yellow;">**type terms**</mark>
  * [falsy](/web/js/val/type/falsy.md)
  * [statically typed](/web/js/val/type/term/static.md)
  * [dynamically typed](/web/js/val/type/term/dynamic.md) - JS is a dynamically typed language.
* <mark style="color:yellow;">**value types**</mark>
  * [primitive](/web/js/val/prim.md)
    * [String](/web/js/val/prim/str.md) <mark style="color:yellow;">**/**</mark> [Number](/web/js/val/prim/num.md) <mark style="color:yellow;">**/**</mark> [Boolean](/web/js/val/prim/boolean.md)
  * [object](/web/js/val/obj.md)
    * [class](/web/js/val/class.md) <mark style="color:yellow;">**/**</mark> [Array](/web/js/val/builtin/arr.md) <mark style="color:yellow;">**/**</mark> [Set](/web/js/val/builtin/set.md) <mark style="color:yellow;">**/**</mark> [Map](/web/js/val/builtin/map.md)
* <mark style="color:yellow;">**helper functions**</mark>
  * [type functions](/web/js/val/type/type-functions.md)
    {% endtab %}

{% tab title="👥 相關" %}

* [typeof](/web/js/val/type/name/typeof.md) <mark style="color:yellow;">**determines**</mark> the [type](/web/js/val/type.md) of a [value](/web/js/val.md). (:point\_right: [type name](/web/js/val/type/name.md))
* [typeName()](/web/js/val/type/name/typename.md)
* [TypeScript](/web/appendix/typescript.md) is a JavaScript dialect that checks types.
  {% endtab %}

{% tab title="📗 參考" %}

* [ ] Eloquent JavaScript > [Types](https://eloquentjavascript.net/08_error.html#h_k7niieKEJG)
  {% endtab %}

{% tab title="📘 手冊" %}

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

{% tab title="🚧" %}

* [ ] type conversion table
* [ ] what is "type" in JS? 🚧
* [ ] how to determine a value's "type"? 🚧
  {% endtab %}
  {% endtabs %}


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