Can webassembly push output to JavaScript?

Say I have a program that is running in webassembly in my browser and I want to take input that the user puts in that program and have it output to other parts of my program. For example, say I want to make a really graphically fancy input box in unity (not that this would ever be practical but just as an example) - can unity take this input that I type in the input box and then output it through webassembly? I could see this as being very cool for custom components, but all the webassembly demos I've seen only take data in to the compiled program (a la flash player or similar).

Thanks!

PS I've asked on SO too, but this is a more open ended question that I think would move we'll with the community here. General webassembly discussion for n00bs also is cool!