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JSX

JSX is a syntax extension for JavaScript that allows writing HTML-like markup inside JavaScript. It has been popularized by React, and then adopted by many other libraries/frameworks.

By default, when running JSX in LiveCodes, React runtime is used. However, other libraries like Preact, nano JSX and others can be used as well (see Custom JSX Runtimes).

TSX is also supported in LiveCodes and is documented here.

Please note that React compiler is also available in LiveCodes and is documented here.

Usage​

The easiest way is to auto-render a component by exporting it as the default export:

You may, however, be more explicit and render the component yourself using React DOM:

note

React's new JSX transform is utilized. So there is no need to import React.

// this is not needed:
// import React from 'react';

export default function App() {
  return <h1>Hello World!</h1>;
}

Auto-rendering​

A component is rendered automatically as a React component (without having to manually use React Dom to render it) if the following conditions are met:

Root Element​

To render the React components to a specific root DOM element use "livecodes-app" as the element id. Otherwise, if that element is not found, a new div element is added to document.body and is used as the root.

Example:

Disabling Auto-rendering​

To disable auto-rendering, set the custom settings disableAutoRender property to true.

Importing Modules​

npm modules can be imported as described in the section about module resolution, including bare module imports and importing from different CDNs. Stylesheet imports are added as <link rel="stylesheet"> tags in the page head.

Example:

Module imports can be customized using import maps as described in module resolution documentations.

Types for Imported Modules​

Types for imported modules are loaded automatically (if available) to provide Intellisense, auto-completion and type information.

LiveCodes Intellisense

LiveCodes Intellisense

Moreover, you can provide custom type definitions for modules that do not have types available on npm. See Custom Types for details.

Exports​

Values exported from script editor (default or named) can be imported in the markup editor by importing from "./script" (with no extension).

This can be useful, for example, when using MDX to import components exported form JSX.

Demo:

show code
import { createPlayground } from 'livecodes';

const options = {
  "params": {
    "mdx": "import Greeting from \"./script\";\n\n<Greeting name=\"MDX\" />\n",
    "jsx": "export default function(props) {\n  return <h1>Greeting from {props.name}!</h1>;\n}\n"
  }
};
createPlayground('#container', options);

note

When values are imported from "./script", auto-rendering is disabled, because it is assumed that you want to take control over component rendering.

Styles​

CSS can be applied to the component using various ways:

Style Editor​

Styles added in the style editor is applied globally to the result page. This can use different languages/processors supported in LiveCodes including CSS, SCSS, Less, Stylus, ..etc. See style documentation for more details.

And of course, styles and stylesheets added in markup editor are also applied globally.

Importing Stylesheets​

Stylesheets imported in script editor are added as <link rel="stylesheet"> tags in the page head. The stylesheet URL can be an absolute URL or a path in the npm package. The URL has to end with ".css".

example:

CSS Modules​

CSS modules are supported and are documented separately. Make sure to enable CSS modules (from style editor menu or in processors property of configuration object).

Demo:

show code
import { createPlayground } from 'livecodes';

const options = {
  "config": {
    "activeEditor": "script",
    "style": {
      "language": "css",
      "content": ".title {\n  color: green;\n  font-family: sans-serif;\n}\n"
    },
    "script": {
      "language": "jsx",
      "content": "import classes from './style.module.css';\n\nexport default function() {\n  return <h1 className={classes.title}>Hello, CSS Modules!</h1>;\n}\n"
    },
    "processors": [
      "cssmodules"
    ]
  }
};
createPlayground('#container', options);

CSS Frameworks​

CSS Frameworks supported in LiveCodes (e.g. Tailwind CSS, UnoCSS, WindiCSS) can detect class names added in JSX. Make sure that the required utility is enabled (from style editor menu or in processors property of configuration object) and that required directives are added to the style editor.

Demo:

show code
import { createPlayground } from 'livecodes';

const options = {
  "config": {
    "activeEditor": "script",
    "style": {
      "language": "css",
      "content": "@tailwind base;\n@tailwind components;\n@tailwind utilities;\n"
    },
    "script": {
      "language": "jsx",
      "content": "export default function() {\n  return <h1 className=\"text-3xl font-bold text-gray-500 text-center m-4\">Hello, Tailwind CSS!</h1>;\n}\n"
    },
    "processors": [
      "tailwindcss"
    ]
  }
};
createPlayground('#container', options);

CSS-in-JS​

CSS-in-JS libraries can be imported and used as usual.

Demo:

show code
import { createPlayground } from 'livecodes';

const options = {
  "params": {
    "jsx": "import styled from 'styled-components';\n\nconst Title = styled.h1`\n text-align: center;\n font-family: sans-serif;\n color: palevioletred;\n`;\n\nexport default function () {\n return <Title>Hello, styled-components!</Title>;\n}\n"
  }
};
createPlayground('#container', options);

Custom JSX Runtimes​

LiveCodes allows using other libraries (like Preact and nano JSX) as the JSX runtime.

JSX is compiled to JavaScript using the TypeScript compiler, which allows multiple configuration options for JSX, including jsx, jsxFactory, jsxFragmentFactory and jsxImportSource.

These can be configured using in-code pragmas or in custom settings.

Example for using Preact:

note

Auto-rendering is disabled for custom JSX runtimes.

Language Info​

Name​

jsx

Extension​

.jsx

Editor​

script

Compiler​

TypeScript compiler

Code Formatting​

Using Prettier.

Custom Settings​

Custom settings added to the property jsx are passed to the TypeScript compiler as compiler options while compiling JSX. In addition, the option disableAutoRender can be set to true to disable auto-rendering.

Please note that custom settings should be valid JSON (i.e. functions are not allowed).

Example:

Custom Settings
{
  "jsx": {
    "disableAutoRender": true,
    "jsxFactory": "h",
    "jsxFragmentFactory": "Fragment"
  }
}
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