To build and use this:

1. Install wasm-pack (if you haven't already):
   ```bash
   curl https://rustwasm.github.io/wasm-pack/installer/init.sh -sSf | sh
   ```
   
2. Build the WASM module: 
   ```bash
   wasm-pack build --target web --out-dir pkg
   ```
   
3. Serve the HTML file using a local HTTP server (required for ES modules): 
   ```bash
   python3 -m http.server 8000
   # or
   npx serve .
   ```

4. Use the API:
   ```js
   try {
       const result = evaluate_cel("name + ' is ' + string(age)", {name: "Alice", age: 30});
       console.log(result);
   } catch (error) {
       console.error(error);
   }
   ```