Is it possible to use a callback in a JSON type?

There are many components in react that are using callback functions inside objects, it seems it's not working with web component JSON format, which is in fact expectable since it's just text, and it can't understand what is the function in the JSON. but would be really nice if we could use function as a object param like this.

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is there any other way other than using the function param only as top level param?