var
  Obj: TJsonObject;
begin
  Obj := TJsonObject.Parse('{ "foo": "bar", "array": [ 10, 20 ] }') as TJsonObject;
  try
    ShowMessage(Obj['foo']);
    ShowMessage(IntToStr(Obj['array'].Count));
    ShowMessage(IntToStr(Obj['array'].Items[0]));
    ShowMessage(IntToStr(Obj['array'].Items[1]));
  finally
    Obj.Free;
  end;
end;

var
  Obj, ChildObj: TJsonObject;
begin
  Obj := TJsonObject.Create;
  try
    // easy access
    Obj['foo'] := 'bar';
    // normal (and faster) access
    Obj.S['bar'] := 'foo';
    // automatic array creation, Obj is the owner of 'array'
    Obj.A['array'].Add(10);
    Obj.A['array'].Add(20);
    // automatic object creation, 'array' is the owner of ChildObj
    ChildObj := Obj.A['array'].AddObject;
    ChildObj['value'] := 12.3;
    // automatic array creation, ChildObj is the owner of 'subarray'
    ChildObj.A['subarray'].Add(100);
    ChildObj.A['subarray'].Add(200);

    ShowMessage(Obj.ToJSON({Compact:=}False));
  finally
    Obj.Free;
  end;

var
  Obj, ClonedObj: TJsonObject;
begin
  Obj := TJsonObject.ParseUtf8('{ "foo": [ "bar", {}, null, true, false, { "key": "value" } ] }') as TJsonObject;
  try
    ClonedObj := TJsonObject.Create;
    try
      // Make a copy of Obj
      ClonedObj.Assign(Obj);
      ShowMessage(ClonedObj.ToJSON(False));
    finally
      ClonedObj.Free;
    end;
  finally
    Obj.Free;
  end;
end;