Unlocking the Power of JavaScript Transpilers: Babel vs SWC

What is Babel?

Babel is a popular transpiler that converts newer JavaScript features, such as ES6 and TypeScript, into older versions like ES5. It’s a powerful tool that helps us write modern JavaScript code while ensuring compatibility with older browsers. Babel’s process involves three major tools:

• parsing
• traversing
• generating code

The Rise of SWC

SWC, written in Rust, is a fast and efficient transpiler that’s gaining popularity. Rust’s reputation for performance and reliability has led many businesses to rewrite parts of their code using this language. For example, Firefox rewrote its CSS renderer, Quantum CSS, in Rust, resulting in substantial performance improvements. Similarly, Tilde rewrote certain parts of its Java HTTP endpoints in Rust, reducing memory usage from 5GB to 50MB.

Why Do We Need Transpilers?

While modern browsers support newer JavaScript features, there are cases where transpilers are necessary. Browsers use different JavaScript engines, such as:

• V8 (Chrome)
• SpiderMonkey (Firefox)
• Chakra (IE)

which means that even with a standard JavaScript specification, support for new features varies widely. Transpilers help us achieve consistent handling of JavaScript code across multiple browsers, ensuring we can use new features without worrying about compatibility issues.

Setting Up SWC

To get started with SWC, you can install it as a package from NPM:

npm install --save-dev @swc/core

Once installed, you can use the CLI tool to transpile your JavaScript files:

npx swc src/index.js -o dist/index.js

You can also integrate SWC into your build system using Webpack. By setting up a webpack.config.js file, you can configure SWC to transpile your JavaScript files:

module.exports = {
  module: {
    rules: [
      {
        test: /\.js$/,
        use: {
          loader: 'wc-loader',
          options: {
            jsc: {
              parser: {
                syntax: 'ecmascript',
                jsx: true,
              },
            },
          },
        },
      },
    ],
  },
};

Configuring SWC

To instruct SWC on how to transpile your files, you need to define a config file called .swcrc. This file allows you to specify settings for transpilation, such as:

• which parser to use
• which options to enable or disable

{
  "jsc": {
    "parser": {
      "syntax": "ecmascript",
      "jsx": true
    }
  }
}

Speed Comparison: Babel vs SWC

When it comes to speed, SWC outperforms Babel significantly. In synchronous mode, SWC is around 20 times faster than Babel, and in asynchronous mode, it’s around 60 times faster. This is because SWC runs on a worker thread, allowing it to scale up with the number of CPU cores.

Here’s a rough estimate of the performance difference:

• Babel (synchronous): 100ms
• SWC (synchronous): 5ms
• Babel (asynchronous): 500ms
• SWC (asynchronous): 8ms