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Excel function: TEXTJOIN

textjoins creates a string where the values of a list or range are separated by given specified character or string. 
textjoin(delimiter, ignore_empty, text1, [text2], …)
textjoin is only available in Office 365.

Quoting values of text-joined range

In order to quote the values of the specified range, that is, to embed those values in apostrophes, the following formula can be used. 
=textjoin( ",", false, """" & L2:N2 & """")

Using a range as separator

It's possible to specify a range that contains the values for the separator:

See also

Excel functions, especially the text and string related ones
Importing and displaying CSV data in Excel
Create comma separated values from a selected Range.
CSV

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