# running execution context

[JS](https://lochiwei.gitbook.io/web/js) ⟩ [concept](https://lochiwei.gitbook.io/web/browser/concepts) ⟩ [execution context](https://lochiwei.gitbook.io/web/js/concept/execution-context) ⟩ running execution context

{% hint style="success" %} <mark style="color:yellow;">**At any point in time**</mark>, there is <mark style="color:red;">**at most**</mark>**&#x20;**<mark style="color:yellow;">**one**</mark> [](https://lochiwei.gitbook.io/web/js/concept/execution-context "mention") that is actually <mark style="color:yellow;">**executing**</mark> code. This is known as the <mark style="color:purple;">**running execution context**</mark>.

📘 [js-spec](https://lochiwei.gitbook.io/web/master/ref/js-spec "mention") ⟩ 8.2 [Execution Contexts](https://262.ecma-international.org/6.0/#sec-execution-contexts)
{% endhint %}

{% tabs %}
{% tab title="⭐️ 重點" %}
{% hint style="success" %}
A <mark style="color:yellow;">**stack**</mark> (call stack) is used to <mark style="color:yellow;">**track**</mark> [](https://lochiwei.gitbook.io/web/js/concept/execution-context "mention")(s). The <mark style="color:purple;">**running execution context**</mark> is always the <mark style="color:yellow;">**top**</mark> element of this stack.
{% endhint %}
{% endtab %}

{% tab title="👥 相關" %}

* [lexical-environment](https://lochiwei.gitbook.io/web/js/concept/execution-context/lexical-environment "mention") is <mark style="color:yellow;">**part**</mark> of <mark style="color:purple;">**execution context**</mark>.
  {% endtab %}

{% tab title="📗 參考" %}

* [ ] Anil ⟩ [Scope, Lexical Environment and Scope Chain in JavaScript](https://medium.com/@anilakgunes/scope-lexical-environment-and-scope-chain-in-javascript-559aadb7dca8) ⭐️
  {% endtab %}

{% tab title="📘 手冊" %}

* [ ] [js-spec](https://lochiwei.gitbook.io/web/master/ref/js-spec "mention") ⟩&#x20;
  * [ ] [Execution Contexts](https://262.ecma-international.org/6.0/#sec-execution-contexts)
  * [ ] [running execution context](https://tc39.es/ecma262/#running-execution-context)
    {% endtab %}

{% tab title="🚧" %}

* [ ] call stack
* [x] running execution context
  {% endtab %}
  {% endtabs %}


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