In this example, the user can enter any number of key-value pairs until they decide to stop, at which point they receive their input back in the form of JSON. Some example input you could enter could include:

name abraham
age 49
fav_colour red
hello world
(press 'Ctrl Z' on Windows or 'Ctrl D' on Unix)

This program begins with the idea that a JSON object without a clearly defined schema is nothing but a HashMap<String, String>[9]. Now, serde_json doesn't accept a String as a value, as that would not be general enough. Instead, it wants a serde_json::Value, which you can easily construct by calling the json! macro on pretty much any type [20].

When we are done, we don't call serde_json::to_string() as before, but use serde_json::to_string_pretty() instead [28], as this results in a less efficient but much more readable JSON. Remember, JSON is not supposed to be primarily read by humans, which is why the default way Serde serialized it is without any whitespace whatsoever. If you're curious about the exact difference, feel free to go ahead and change to_string_pretty() to to_string() and compare the results.