jsBoolean

jsBoolean = 2

Example

function ReadStrictBoolean(Value: TJSONValue): Boolean;
begin
  Result := (Value.ValueType = jsBoolean) and
            Value.NotNull and
            Value.AsBoolean;
end;

Usage

jsBoolean identifies a Velox TJSONBoolean whose stored value is true or false independently of its mutable null flag.

Additional Technical Info

jsBoolean is ordinal 2 of TJSONValueType. It is assigned to concrete TJSONBoolean objects; their AsString form is lowercase true or false when not null.

Check ValueType when Boolean syntax matters. TJSONValue.AsBoolean is deliberately permissive for other scalar classes: it compares their string case-insensitively with true, and every other non-Boolean text becomes false without an invalid-value error. Null also becomes false. Without a kind/null check, malformed text, JSON false and null collapse to the same result.

The Deltics parser accepts true and false case-insensitively, although RFC 8259 requires those literals to be lowercase. Serialization normalizes a concrete Boolean to lowercase. A newly constructed TJSONBoolean is non-null false by default.

Scalar null state is separate from the enum. Clear sets IsNull but does not erase the stored Boolean. Assigning Value/AsBoolean clears null state, and manually setting IsNull := False can reveal the old stored value. Use both ValueType and IsNull/NotNull when input provenance matters.

The example is source-reviewed only; no JSON parsing, Boolean conversion, runtime or image test ran.

Related Code Library entries

• jsNull - concrete JSON null.
• jsString - text that permissive AsBoolean can convert.
• TJSONValue.AsBoolean - conversion accessor.

External references

• RFC 8259 literal names.

Created 2026-07-15