TEXTJOIN( delimiter, skip_empty, string1[, string2][, …] )
delimiter is a text string and can be a range.
skip_empty is a logical (TRUE or FALSE, 1 or 0) argument. When TRUE, empty strings will be ignored.
string1[, string2][, …] are strings or references to cells or ranges that contains text to join.
Ranges are traversed row by row (from top to bottom).
If delimiter is a range, the range need not be of the same size as the number of strings to be joined.
If there are more delimiters than strings to be joined, not all delimiters will be used.
If there are less delimiters than strings to be joined, the delimiters will be used again from the start.
=TEXTJOIN(" ",TRUE, "Here", "comes", "the", "sun") returns "Here comes the sun" with space character as delimiter and empty strings are ignored.
if A1:B2 contains "Here", "comes", "the", "sun" respectively, =TEXTJOIN("-",TRUE,A1:B2) returns "Here-comes-the-sun" with dash character as delimiter and empty strings are ignored.