Use path module in node.js returns the platform-specific file separator.
example

path.sep  // on *nix evaluates to a string equal to "/"

Edit: As per Sebas's comment below, to use this, you need to add this at the top of your js file:

const path = require('path')

Afair you can always use / as a path separator, even on Windows.

Quote from http://bytes.com/forum/thread23123.html:

So, the situation can be summed up rather simply:

• All DOS services since DOS 2.0 and all Windows APIs accept either forward slash or backslash. Always have.

• None of the standard command shells (CMD or COMMAND) will accept forward slashes. Even the "cd ./tmp" example given in a previous post fails.

The Correct Answer

Yes all OS's accept CD ../ or CD ..\ or CD .. regardless of how you pass in separators. But what about reading a path back. How would you know if its say, a 'windows' path, with ' ' and \ allowed.

The Obvious 'Duh!' Question

What happens when you depend on, for example, the installation directory %PROGRAM_FILES% (x86)\Notepad++. Take the following example.

var fs = require('fs');                             // file system modulevar targetDir = 'C:\Program Files (x86)\Notepad++'; // target installer dir// read all files in the directoryfs.readdir(targetDir, function(err, files) {    if(!err){        for(var i = 0; i < files.length; ++i){            var currFile = files[i];            console.log(currFile);             // ex output: 'C:\Program Files (x86)\Notepad++\notepad++.exe'            // attempt to print the parent directory of currFile            var fileDir = getDir(currFile);            console.log(fileDir);              // output is empty string, ''...what!?        }    }});function getDir(filePath){    if(filePath !== '' && filePath != null){       // this will fail on Windows, and work on Others       return filePath.substring(0, filePath.lastIndexOf('/') + 1);    }}

What happened!?

targetDir is being set to a substring between the indices 0, and 0 (indexOf('/') is -1 in C:\Program Files\Notepad\Notepad++.exe), resulting in the empty string.

The Solution...

This includes code from the following post: How do I determine the current operating system with Node.js

myGlobals = { isWin: false, isOsX:false, isNix:false };

Server side detection of OS.

// this var could likely a global or available to all parts of your appif(/^win/.test(process.platform))     { myGlobals.isWin=true; }else if(process.platform === 'darwin'){ myGlobals.isOsX=true; }else if(process.platform === 'linux') { myGlobals.isNix=true; }

Browser side detection of OS

var appVer = navigator.appVersion;if      (appVer.indexOf("Win")!=-1)   myGlobals.isWin = true;else if (appVer.indexOf("Mac")!=-1)   myGlobals.isOsX = true;else if (appVer.indexOf("X11")!=-1)   myGlobals.isNix = true;else if (appVer.indexOf("Linux")!=-1) myGlobals.isNix = true;

Helper Function to get the separator

function getPathSeparator(){    if(myGlobals.isWin){        return '\\';    }    else if(myGlobals.isOsx  || myGlobals.isNix){        return '/';    }    // default to *nix system.    return '/';}// modifying our getDir method from above...

Helper function to get the parent directory (cross platform)

function getDir(filePath){    if(filePath !== '' && filePath != null){       // this will fail on Windows, and work on Others       return filePath.substring(0, filePath.lastIndexOf(getPathSeparator()) + 1);    }}

getDir() must be intelligent enough to know which its looking for.

You can get even really slick and check for both if the user is inputting a path via command line, etc.

// in the body of getDir() ...var sepIndex = filePath.lastIndexOf('/');if(sepIndex == -1){    sepIndex = filePath.lastIndexOf('\\');}// include the trailing separatorreturn filePath.substring(0, sepIndex+1);

You can also use 'path' module and path.sep as stated above, if you want to load a module to do this simple of a task. Personally, i think it sufficient to just check the information from the process that is already available to you.

var path = require('path');var fileSep = path.sep;    // returns '\\' on windows, '/' on *nix

And Thats All Folks!