How to escape backslash in JavaScript?

Question

I want to replace backslash => '\' with secure \ replacement.

But my code replacing all '#' fails when applied for replacing '\':

el = el.replace(/\#/g, '&#35;'); // replaces all '#' //that's cool
el = el.replace(/\\/g, '&#92;'); // replaces all '\' //that's failing

Why?

The code you posted works just fine. Are you sure that `el` contains `'\'` characters? — zzzzBov, Oct 12 '12 at 20:18
Can you give us a test case where it is failing, seems to work for me on a simple test case. — Akshet, Oct 12 '12 at 20:20
In that script you already use encodeURIComponent() which replaces any backslashes with %5C. I think you don't need the two manual replacements. — Wolfgang Stengel, Oct 12 '12 at 20:28
FYI `#` doesn't need to be escaped; `el.replace(/#/g, '#')` should work. And also your code to replace backslashes works fine here. — NullUserException, Oct 12 '12 at 21:04

score 18 · Accepted Answer · answered Oct 15 '12 at 21:03

18

open console and type

'\'.replace(/\\/g, '&#92;');

fails because the slash in the string isn't really in the string, it's escaping '

'\\'.replace(/\\/g, '&#92;');

works because it takes one slash and finds it.

your regex works.

answered Oct 15 '12 at 21:03

dansch

1

so how do you handle "domain\user" then? you got to first replace single backslash to double and then use .replace(/\\/g, '\'); ? – HaBo Apr 07 '16 at 09:23
`/\\/g` looks for a single backslash. At no point are we replacing a single with a double. The first backslash escapes the second one, so this regex looks for a single backslash, globally. to handle "domain\user", `/\\/g` should work fine. – dansch Apr 14 '16 at 14:00

score 2 · Answer 2 · edited Sep 30 '17 at 19:35

2

You can use String.raw to add slashes conveniently into your string literals. E.g. String.raw`\a\bcd\e`.replace(/\\/g, '\');

edited Sep 30 '17 at 19:35

Alan Pierce

answered May 10 '16 at 10:30

Tamas Rev

2 Answers2