javascript, replace \n with \r\n
javascript, regex
Solution
Simply make the `\r` an optional part of the match, then you can replace with impunity:
"Hello\r\nWorld\n".replace(/\r?\n/g, "\r\n")
Problem
I need to replace all `\n` with `\r\n`, but only if `\n` hasn't already `\r` previosly. i.e. `Hello\nGreat\nWorld` -> `Hello\r\nGreat\r\nWorld` `Hello\r\nGreat\r\nWorld` -> `Hello\r\nGreat\r\nWorld`. In Java i can do it in next way ``` "Hello\nGreat\nWorld".replaceAll("(?<!\r)\n", "\r\n"); ``` But `(?<!X)` construct is absent in JS. Any ideas, how can I do it in JS?