# function name scope

[JS](/web/js.md)⟩ [scope](/web/js/scope.md) ⟩ function name scope

{% hint style="success" %}
the <mark style="color:yellow;">**name**</mark> [identifier](/web/js/grammar/token/id.md) of a [function expression](/web/js/val/func/expr.md) is in <mark style="color:yellow;">**its own**</mark> <mark style="color:purple;">**function name scope**</mark>, nested <mark style="color:orange;">**between**</mark> the <mark style="color:yellow;">**outer enclosing scope**</mark> and the <mark style="color:yellow;">**inner function scope**</mark>.
{% endhint %}

{% tabs %}
{% tab title="💈範例" %}

* replit：[function expression identifier](https://replit.com/@pegasusroe/function-expression-identifier#index.js)

```javascript
var outerName = function innerName() {

    // ⭐ shadowing `innerName` is allowed inside function body
    // -----------------------------------------------------------------------
    // if `innerName` was in the function's scope, we'd expect an error here:
    // namely, SyntaxError: Identifier 'innerName' has already been declared
    let innerName = 1234;
    
    return innerName;
};

outerName(),    // 1234
```

👉 [⛔️ SyntaxError](/web/js/err/syntax.md) ⟩ [identifier 'xxx' has already been declared❗️](/web/js/err/syntax/redeclare.md)
{% endtab %}

{% tab title="📗 參考" %}

* [ ] [YDKJS: Scope & Closures (v.2)](/web/master/ref/book/you-dont-know-js-series-v.2/ydkjs-scope-and-closures-v.2.md) ⟩ Appendix A: [Exploring Further](https://github.com/getify/You-Dont-Know-JS/blob/2nd-ed/scope-closures/apA.md#appendix-a-exploring-further)
  {% endtab %}
  {% endtabs %}


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