What is JSX Transform in React? Understanding the New JSX Runtime

JSX Transform

JSX transform is a process that converts JSX syntax into regular JavaScript code that browsers can understand. JSX makes it easier to write and visualize React components. It allows you to write code like this:

const element = <h1>Hello, World!</h1>;

However, browsers don’t understand JSX directly because it’s not valid JavaScript. Instead, JSX needs to be transformed into standard JavaScript, such as:

const element = React.createElement("h1", null, "Hello, World!");

This transformation is what the JSX transform does.

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How JSX Transform Works

Let us understand how the below JSX is transformed,

const App = () => (
  <div>
    <h1>Welcome</h1>
    <p>This is a JSX transform example.</p>
  </div>
);

Old Transform JSX Syntax

import React from "react";

function App() {
  return React.createElement(
    "div",
    null,
    React.createElement("h1", null, "Welcome"),
    React.createElement("p", null, "This is a JSX transform example.")
  );
}

New Transform using JSX Runtime

With React 17, the new JSX runtime introduces jsx and jsxs functions for creating elements: - jsx is used for single children. - jsxs is used for multiple children.

import { jsx, jsxs } from "react/jsx-runtime";

const App = () =>
  jsxs("div", {
    children: [jsx("h1", { children: "Welcome" }), jsx("p", { children: "This is a JSX transform example." })],
  });

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Benefits Of JSX Runtime

1. Cleaner Code: You no longer need to import React explicitly when using JSX, making your code cleaner and simpler.
2. Improved Performance: The new JSX transform can generate optimized code for modern JavaScript runtimes.
3. Backward Compatibility: It’s fully backward-compatible, meaning you can still use the old React.createElement approach if needed.
4. Reduced Bundle Size: By only importing the parts of React that are needed, the new transform can help reduce the size of your application bundle.

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Setting Up The JSX Transform

To enable the JSX transform using JSX runtime, you need to configure your build tools like Babel.

For example: Add the @babel/preset-react with the runtime option set to "automatic":

// **Babel Configuration:**
{
  "presets": [["@babel/preset-react", { "runtime": "automatic" }]]
}

This tells Babel to use the new JSX transform, which automatically imports the required runtime functions.