{ 013: "11" } isn't valid JSON. All object keys in JSON must be strings. And if you try to do that in value position, it's still not a problem because JSON never treats unquoted text as a string.
Also JSON doesn't treat a 0 prefix on a number as special. There are no octal (or hex) literals in JSON. In fact, a JSON number literal cannot even start with 0 unless that's the only digit (before the period), e.g. 013 is not a valid numeric literal in JSON.
Also JSON doesn't treat a 0 prefix on a number as special. There are no octal (or hex) literals in JSON. In fact, a JSON number literal cannot even start with 0 unless that's the only digit (before the period), e.g. 013 is not a valid numeric literal in JSON.