This example demonstrates a browser-based file system hack for the esbuild-wasm package, enabling it to read and write files in memory. It implements a virtual filesystem using Node.js `fs` APIs, including file handles, metadata, and directory structures. The code intercepts esbuild's internal `fs.writeSync` and `fs.read` calls to route file operations through a custom `FS` object, allowing the bundler to process input files and analyze their sizes. It uses TypeScript and relies on the `decode` and `encode` utilities to handle file content.