This JSON (taken from https://www.w3schools.com/js/js_json_intro.asp):

    {"name":"John", "age":30, "car":null}

could be this S-expression:

    ((name John)
     (age 30)
     (car ()))

The canonical representation (suitable for cryptographic hashing) would be ((4:name4:John)(3:age2:30)(3:car())).