# JSX (/docs/runtime/jsx)
Related: [Watch Mode](/docs/runtime/watch-mode.md), [Debugging](/docs/runtime/debugger.md), [REPL](/docs/runtime/repl.md), [bunfig.toml](/docs/runtime/bunfig.md), [File Types](/docs/runtime/file-types.md), [Module Resolution](/docs/runtime/module-resolution.md)
Bun supports `.jsx` and `.tsx` files. Bun's internal transpiler converts JSX syntax into vanilla JavaScript before execution.
```ts react.tsx icon="/icons/typescript.svg"
function Component(props: {message: string}) {
return (
{props.message}
);
}
console.log();
```
## Configuration [#configuration]
Bun reads your `tsconfig.json` or `jsconfig.json` to determine how to perform the JSX transform internally. If you'd rather not use either, you can set the same options in [`bunfig.toml`](/runtime/bunfig).
Bun respects the following compiler options.
### [`jsx`](https://www.typescriptlang.org/tsconfig#jsx) [#jsx]
How JSX constructs are transformed into vanilla JavaScript internally. The following table lists the possible values of `jsx`, along with how each transpiles this JSX component:
```tsx
Hello
```
| Compiler options | Transpiled output |
| --------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `json
{
"jsx": "react"
}
` | `tsx
React.createElement(Box, { width: 5 }, "Hello");
` |
| `json
{
"jsx": "react-jsx"
}
` | `tsx
import { jsx } from "react/jsx-runtime";
jsx("Box", { width: 5 }, "Hello");
` |
| `json
{
"jsx": "react-jsxdev"
}
` | `tsx
import { jsxDEV } from "react/jsx-dev-runtime";
jsxDEV(
"Box",
{ width: 5, children: "Hello" },
undefined,
false,
undefined,
this,
);
`
The `jsxDEV` variable name is a React convention. The `DEV` suffix marks code intended for development. The development version of React is slower and includes additional validity checks & debugging tools. |
| `json
{
"jsx": "preserve"
}
` | `tsx
// JSX is not transpiled
// "preserve" is not supported by Bun currently
Hello
` |
### [`jsxFactory`](https://www.typescriptlang.org/tsconfig#jsxFactory) [#jsxfactory]
Only applicable when
`jsx`
is
`react`
.
The function name used to represent JSX constructs. Default value is `"React.createElement"`. Set this for libraries like [Preact](https://preactjs.com/) that use a different function name (`"h"`).
| Compiler options | Transpiled output |
| --------------------------------------------------------------------- | --------------------------------------------- |
| `json
{
"jsx": "react",
"jsxFactory": "h"
}
` | `tsx
h(Box, { width: 5 }, "Hello");
` |
### [`jsxFragmentFactory`](https://www.typescriptlang.org/tsconfig#jsxFragmentFactory) [#jsxfragmentfactory]
Only applicable when
`jsx`
is
`react`
.
The function name used to represent [JSX fragments](https://react.dev/reference/react/Fragment) such as `<>Hello`. Default value is `"React.Fragment"`.
| Compiler options | Transpiled output |
| ------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------ |
| `json
{
"jsx": "react",
"jsxFactory": "myjsx",
"jsxFragmentFactory": "MyFragment"
}
` | `tsx
// input
<>Hello;
// output
myjsx(MyFragment, null, "Hello");
` |
### [`jsxImportSource`](https://www.typescriptlang.org/tsconfig#jsxImportSource) [#jsximportsource]
Only applicable when
`jsx`
is
`react-jsx`
or
`react-jsxdev`
.
The module the component factory function (such as `createElement`, `jsx`, or `jsxDEV`) is imported from. Default value is `"react"`. You'll typically need this when using a component library like Preact.
| Compiler options | Transpiled output |
| ---------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `jsonc
{
"jsx": "react-jsx",
// jsxImportSource is not defined
// default to "react"
}
` | `tsx
import { jsx } from "react/jsx-runtime";
jsx("Box", { width: 5, children: "Hello" });
` |
| `jsonc
{
"jsx": "react-jsx",
"jsxImportSource": "preact",
}
` | `tsx
import { jsx } from "preact/jsx-runtime";
jsx("Box", { width: 5, children: "Hello" });
` |
| `jsonc
{
"jsx": "react-jsxdev",
"jsxImportSource": "preact",
}
` | `tsx
// /jsx-runtime is automatically appended
import { jsxDEV } from "preact/jsx-dev-runtime";
jsxDEV(
"Box",
{ width: 5, children: "Hello" },
undefined,
false,
undefined,
this,
);
` |
### JSX pragma [#jsx-pragma]
You can set any of these values per file with a *pragma*, a comment that sets a compiler option in a particular file.
| Pragma | Equivalent config |
| ---------------------------------------- | ------------------------------------------------------------------ |
| `ts
// @jsx h
` | `jsonc
{
"jsxFactory": "h",
}
` |
| `ts
// @jsxFrag MyFragment
` | `jsonc
{
"jsxFragmentFactory": "MyFragment",
}
` |
| `ts
// @jsxImportSource preact
` | `jsonc
{
"jsxImportSource": "preact",
}
` |
## Logging [#logging]
Bun implements special logging for JSX to make debugging easier. Given the following file:
```tsx index.tsx icon="/icons/typescript.svg"
import { Stack, UserCard } from "./components";
console.log(
,
);
```
Bun pretty-prints the component tree:
## Prop punning [#prop-punning]
The Bun runtime also supports "prop punning" for JSX: a shorthand for assigning a variable to a prop with the same name.
```tsx react.tsx icon="/icons/typescript.svg"
function Div(props: {className: string;}) {
const {className} = props;
// without punning
return ;
// with punning
return ;
}
```