Try using the heredoc syntax:
myString = """
answer
to life
the universe
and everything
is
#{40+2}
"""
This converts to this javascript:
var myString;
myString = "answer\nto life\nthe universe\nand everything\nis\n" + (40 + 2);
There’s not really any point to make it actually be on newlines in the compiled javascript visually, is there?