ExportString

ExportString[expr, "format"] generates a string of expr in the specified format.

Examples

Export to JSON string:

ExportString[{1, 2, 3}, "JSON"]
(* "[1, 2, 3]" *)

Export to CSV:

ExportString[{{1, 2}, {3, 4}}, "CSV"]
(* "1,2\n3,4" *)

Please visit the official Wolfram Language Reference for more details.