Why are web workers not allowed to modify the dom

I know web workers work as a separate thread than the UI thread but i dont understand why they are not allowed to modify the DOM. I mean that you can allow inter thread communication and keep the DOM data in a shared space and have the web workers threa开发者_StackOverflowd modify the DOM. Why is this not allowed in browsers?

Because the DOM is not threadsafe, and JavaScript does not expose a thread API.

See also:

• Is JavaScript multithreaded?
• Thread Safety in Javascript?
• Using web workers - About thread safety