3. Null and booleans
Readable Object Notation

null represents an explicit empty value. A map member whose value is null is still present in the map. true and false are the two boolean values. These spellings are case-sensitive. Quoting one of them produces a string instead.

[null true false "null" "true" "false"]

[null true false "null" "true" "false"]

[
  null,
  true,
  false,
  "null",
  "true",
  "false"
]