Replace double backslashes with a single backslash in javascript

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?

Solution

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;
}