Joining strings in lists of strings

Question

I have a list:

lis = {{"abc","def","ghi"},{"jkl","mno"}}

and wish to get:

res = {"abc def ghi","jkl mno"}

This:

Table[StringJoin[lis[[i]]], {i, Length[lis]}]

doesn't produce the desired " " between the original elements in lis. As always, thanks for suggestions!

Answer 1

You can use StringRiffle:

StringRiffle /@ lis

{"abc def ghi", "jkl mno"}

Answer 2

Use Riffle

lis = {{"abc", "def", "ghi"}, {"jkl", "mno"}};

StringJoin[Riffle[#, " "]] & /@ lis

(* {"abc def ghi", "jkl mno"} *)