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
– zzzzBov, Commented Oct 12, 2012 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
– Akshet, Commented Oct 12, 2012 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
– Wolfgang Stengel, Commented Oct 12, 2012 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
– NullUserException, Commented Oct 12, 2012 at 21:04

dansch · Accepted Answer · 2012-10-15 21:03:01Z

19

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, 2012 at 21:03

dansch

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2 Comments

HaBo Over a year ago

so how do you handle "domain\user" then? you got to first replace single backslash to double and then use .replace(/\\/g, '\'); ?

dansch Over a year ago

/\\/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.

Alan Pierce · Accepted Answer · 2017-09-30 19:35:46Z

4

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, 2017 at 19:35

Alan Pierce

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answered May 10, 2016 at 10:30

Tamas Rev

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