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Tweak the @as decorator syntax widget docs #1011

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May 3, 2025
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Tweak the @as decorator syntax widget docs #1011

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33 changes: 32 additions & 1 deletion misc_docs/syntax/decorator_as.mdx
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Expand Up @@ -6,7 +6,10 @@ summary: "This is the `@as` decorator."
category: "decorators"
---

The `@as` decorator is commonly used on record types to alias record field names to a different JavaScript attribute name.
The `@as` decorator has multiple uses in ReScript.

## Change runtime name of record field
The `@as` decorator can be used on record types to alias record field names to a different JavaScript attribute name.

This is useful to map to JavaScript attribute names that cannot be expressed in ReScript (such as keywords).

Expand Down Expand Up @@ -52,8 +55,36 @@ var value = [

</CodeTab>

## Change the runtime representation of a variant constructor
Similarily to changing the runtime name of a record field, you can change the runtime representation of a variant constructor using `@as()`. Only with variants, you have many more options for the runtime representation than for record field names:

<CodeTab labels={["ReScript", "JS Output"]}>

```res
@unboxed
type pet = | @as("dog") Dog | @as(1) Cat | @as(null) SomethingElse

let dog = Dog
let cat = Cat
let somethingElse = SomethingElse

```

```js
let dog = "dog";

let cat = 1;

let somethingElse = null;
```

</CodeTab>

Read more about the [`@as` decorator and variants](variant.md#valid-as-payloads).

### References

* [Bind Using ReScript Record](/docs/manual/latest/bind-to-js-object#bind-using-rescript-record)
* [Constrain Arguments Better](/docs/manual/latest/bind-to-js-function#constrain-arguments-better)
* [Fixed Arguments](/docs/manual/latest/bind-to-js-function#fixed-arguments)
* [`@as` decorator and variants](variant.md#valid-as-payloads)