How to check if a value is literally null

  arduinojson, c++, null

I have an JSON object like this:

{ "foo": null }

How do I check if the value of foo is a literal null. I found the function JsonObject::isNull() but that apparently is for

testing whether the JsonObject points to an object or not

That is not what I want my code to check, but I couldn’t find a solution to this problem.

Source: Windows Questions C++