JavaScript - What is correct way for replace "\" charcter with "/" in RegExp

Question

I defined a function in JavaScript that replace all -, _, @, #, $ and \ (they are possible separators) with / (valid separator).

My goal is any string like "1394_ib_01#13568" convert to "1394/ib/01/13568"

function replaceCharacters(input) {

    pattern_string = "-|_|@|#|$|\u005C";      // using character Unicode
    //pattern_string = "-|_|@|#|$|\";         // using original character
    //pattern_string = "-|_|@|#|$|\\";        // using "\\"
    //pattern_string = "\|-|_|@|#|$";         // reposition in middle or start of string
    pattern = new RegExp(pattern_string, "gi");

    input = input.replace(pattern, "/");
    return input;
}

My problem is when a string with \ character send to function result is not valid.

I tried use Unicode of \ in define pattern, Or use \\\ instead of it. Also I replaced position of it in pattern string. But in any of this situation, problem wasn't solved and browser return invalid result or different error such as:

SyntaxError: unterminated parenthetical    ---> in using "\u005C"
SyntaxError: \ at end of pattern           ---> in using "\\"
Invalid Result: broken result in 2 Line or replace with undefined character based on input string (the character after "\" determine result)
                        ---> in reposition it in middle or start of pattern string

Answer 1

var pattern_string = "-|_|@|#|\\$|\\\\";

You have to escape the slash once for the pattern, so it'll try to match the literal character:

\\

Then, escape each slash again for the string literal:

"\\\\"

Also note that I added an escape for the $. To match a dollar sign literally, it'll needs to be escaped as well, since it normally represents an anchor for the "end of the line/string."

---

You can also use a Regex literal to avoid the string, using only the escape sequences necessary for the pattern:

var pattern = /-|_|@|#|\$|\\/gi;

And, as you're matching only single characters, you can use a character class instead of alternation:

var pattern = /[-_@#\$\\]/gi;

(Just be careful with the placement of the - here. It's fine as the first character in the class, but can represent a range of characters when placed in the middle. You can also escape it to ensure it doesn't represent a range.)