how i can produce this json with the jbuilder DSL

{ data: undefined }

I think it is necessary to precise without explaining why that { data: null } or { } are not the same json as the first

CodePudding user response：

According to

It means that undefined is not supported by JSON

See also JSON site

In any case, sending undefined data from the backend to the frontend is quite strange. I believe that if there is such a need, it is better to use null value or even not send anything