Only remove the last newline characters (\n):
verses1 = "1\n222\n"
verses1.replace(/\n$/, "")
// "1\n222"
verses2 = "1\n222\n\n"
verses2.replace(/\n$/, "")
// "1\n222\n"
Only all the last newlines (\n):
verses = "1\n222\n\n"
verses.replace(/\n+$/, "")
// "1\n222"
https://regexr.com/4uu1r