---
title: "JavaScript"
description: "newt/ui is written in TypeScript, but the CLI can write plain JavaScript into a project that does not use it."
---

The registry is TypeScript. If your project is not, set `typescript` to `false`
in [`components.json`](/docs/components-json) — `newtui init` asks, and answering
no sets it for you — and every file the CLI writes afterwards is JavaScript.

```json title="components.json"
{
  "typescript": false,
  "aliases": {
    "components": "@/components",
    "ui": "@/components/ui",
    "utils": "@/lib/utils"
  }
}
```

## What the CLI strips [#strips]

The transform is textual and deliberately small, because the components are
written so that it can be. It removes:

- type annotations on parameters, variables and return values;
- `interface` and `type` declarations;
- `import type` statements and the type-only specifiers inside a mixed import;
- `satisfies` and `as` expressions;
- generic parameter lists on functions and components.

Runtime code is untouched. The `cva` variant definitions, the `cn` calls and the
class strings are the same in both languages — the types they carried were
inferred from the same objects.

<div data-framework="react">

The extension follows `tsx`: with `typescript: false` the CLI writes
`components/ui/button.jsx`.

</div>

<div data-framework="vue">

The single file components keep the `.vue` extension and lose
`lang="ts"` from their `<script setup>` block. The `index.ts` barrel becomes
`index.js`.

</div>

## What you give up [#tradeoffs]

`VariantProps` is how a React or Vue component states which variants exist. In
JavaScript that contract is gone: passing `variant="brand"` to a button that has
no such variant is a silent no-op rather than a type error.

The component pages on this site list every variant for exactly that reason —
they are the reference a JavaScript project reads instead of the types.

> **Info**
>
> The plain HTML and CSS build has no language question at all: it is class
> names on markup. See [HTML &amp; CSS](/docs/html-css).