> For the complete documentation index, see [llms.txt](https://bimwhale.gitbook.io/ifc-js/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://bimwhale.gitbook.io/ifc-js/developer-guide/step-by-step/parse-the-ifc-file-inside-a-web-worker.md).

# Parse the IFC

This is where the fun begins!

We are going to modify the orignal source code. Take a look at `IFC.js`.

{% code title="src/IFC.js" %}

```javascript
function loadIfc(ifcData) {
    const loaded = loadIfcFileItems(ifcData);
    const structured = constructProject(loaded);
    return buildGeometry(structured);
}
```

{% endcode %}

As we discuessed earlier, we cannot build the entire gemoetry inside the `Web Worker`. 

{% code title="example/web-worker/worker/worker.js" %}

```javascript
onmessage = (e) => {
    const ifcData = e.data; 
    const loaded = IFCjs.loadIfcFileItems(ifcData);
    const structured = IFCjs.constructProject(loaded);
    postMessage(structured);
};
```

{% endcode %}

If we run this code, it won't work. The Web Worker has no idea what `IFC.js` is. We must [import the scripts](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Using_web_workers#importing_scripts_and_libraries).

{% code title="example/web-worker/worker/worker.js" %}

```javascript
importScripts('../../build/IFC.js');
onmessage = (e) => {
    const ifcData = e.data; 
    const loaded = IFCjs.loadIfcFileItems(ifcData);
    const structured = IFCjs.constructProject(loaded);
    postMessage(structured);
};
```

{% endcode %}

Again, please note that this will not work! The `Web Worker` will complain that [Three](https://threejs.org) and [Chevrotain](https://github.com/SAP/chevrotain) is missing.

Again, to clarify - **WE CANNOT USE THREE INSIDE THE WEB WORKER.**