I'll add something: if a string [^1] contains essentially only ASCII [^2] characters v8 will use 1 byte per character, if that string contains _any_ character other than ASCII characters in it then it will use 2 bytes for each character in the string. Said it differently storing strings as lines may save you up to 50% of memory usage depending on your use case.
[^1]: It actually depends on how that string was made, if internally it still references the parent string then slicing it up into lines won't save you any memory. I'm referring to "flattened" strings.
[^2]: I don't remember what the exact character set is, I think it's not exactly ASCII but close enough.