You can use existing e.g C# libraries on the client side (browser)

e.g you can develop parser in console application and then ship it to the browser and use it there to parse e.g code without changing a single line of code or having to do some bullshit or traspiling it to js.

Once it matures it will allow you to get rid of writing javascript and use java, c#, rust, c++ and many other to write frontend.