Replace double backslashes with a single backslash in javascript

Question

I have the following problem:

I have a script that executes an AJAX request to a server, the server returns C:\backup\ in the preview. However, the response is "C:\\backup\\". Not really a big deal, since I just thought to replace the double slashes with single ones. I've been looking around here on stack, but I could only find how to replace single backslashes with double ones, but I need it the other way around.

Can someone help me on this matter?

KooiInc · Accepted Answer · 2023-01-24T11:10:08.833

This should do it: "C:\\backup\\".replace(/\\\\/g, '\\')

In the regular expression, a single \ must be escaped to \\, and in the replacement \ also.

[edit 2021] Maybe it's better to use template literals.

console.log(`original solution ${"C:\\backup\\".replace(/\\\\/g, '\\')}`)

// a template literal will automagically replace \\ with \
console.log(`template string without further ado ${`C:\\backup\\`}`);

// but if they are escaped themselves
console.log(`Double escaped ${`C:\\\\backup\\\\`.replace(/\\{2,}/g, '\\')}`);

// multiple escaped
console.log(`multiple escaped ${`C:\\\\\\\\backup\\\\`
  .replace(/\\{2,}/g, '\\')}`);

// don't want to replace the last \\
console.log(`not the last ${`C:\\\\\\backup\\\\`
  .replace(/\\{2,}([^\\{2,}$])/g, (a ,b) => a.slice(0,1) + b)}` );

// don't want to replace the first \\
console.log(`not the first ${`C:\\\\backup\\`.replace(/\\[^\\]$/g, '\\')}`);

// a generic tagged template to replace all multiple \\ OR //
const toSingleSlashes = (strs, ...args) => 
  strs.reduce( (a, v, i ) => 
    a.concat(args[i-1] || ``).concat(v, ``), `` )
      .replace( /(\\|\/){2,}/g, (a, b) => b );

console.log(`generic tagged template 1 ${
  toSingleSlashes`C:\\backup\\`}`);

console.log(`generic tagged template 2 ${
  toSingleSlashes`C:\\\\\\\\backup\\\\\\\\\\`}`);
  
console.log(`generic tagged template 3 ${
  toSingleSlashes`C:\\\\\\\\backup\\`}`);
  
console.log(`generic tagged template 4 ${
  toSingleSlashes`C:////////backup////`}`);

console.log(`reply to comment @chitgoks => 
"test\\\\hehehe" is by default "test\\hehehe"
so, no replacement necessary here ...`);

.as-console-wrapper {
    max-height: 100% !important;
}

I have double backslash in original regex which when escaped boils down to four backslashes. Now, when I tried your regex, it converts those four backslashes to single backslash instead of double. What can I do to prevent it? — HalfWebDev, Aug 07 '19 at 05:49
@codemirror you don't need any replacement: the string `ab\cd` itself will not contain a slash, (\c = (escape)c). Try `console.log("ab\cd")` in the developer console. — KooiInc, Apr 19 '21 at 15:44
@chitgoks See edited answer (run snippet, see bottom of the logging) — KooiInc, Jan 24 '23 at 11:10

xxbinxx · Answer 2 · 2023-02-05T10:31:02.363

4

Best is to use regex to replace all occurrences:

C:\\backup\\".replace(/\/\//g, "/")[0]

this returns: C:\backup\

OR

use split()

"C:\\backup\\".split();

both produces your desired result

C:\backup\

console.log("using \"C:\\backup\\\".replace(/\/\//g, \"/\")")
console.log("C:\\backup\\".replace(/\/\//g, "/"));

console.log("Using \"C:\\backup\\\".split()");
console.log("C:\\backup\\".split()[0]);

edited Feb 05 '23 at 10:31

answered Aug 14 '14 at 09:28

xxbinxx

1,527
11
18

Just wanted to note this will work with forward slash but not back slash – Sami Fouad Feb 03 '17 at 04:22
This will also remove any single slash 'ab\cd' --> abcd – codemirror Sep 12 '17 at 11:49
1

@codemirror Good point. But if it contains '\' then you won't see it as 'ab\cd' you'll get that as 'ab\\cd' in code. – xxbinxx Nov 20 '17 at 05:33
Your snippet `"C:\\backup\\".split();` does not work when testing it in the Chrome console. In addition, it would be more appropriate to write `"C:\\backup\\".split()[0]` to directly obtain the wanted string. – Pieber Nov 04 '22 at 17:36

score 0 · Answer 3 · answered Jun 07 '23 at 16:33

I think everyone might be misleading themselves the console.log(). It will automatically display the expected result, regardless of whether or not you replace any of the characters.

const test = 'C:\\';
console.log( test ) // this will write out "C:\"
console.log( `${ test.replace( /\\{2,}/g, '\\' }` ) // this will also write out "C:\"

The string value is still single character escaped. However, the console.log is hiding that fact from you.

From what I can tell, there is no way to actually replace the \\ with \ in javascript.

the closest you can get would be to do something like this, however its still interpreted the same way

test.replace( /\\{2,}/g, '\u005C' )

Replace double backslashes with a single backslash in javascript

3 Answers3

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