Node.js check exist file

Why not just try opening the file ? fs.open('YourFile', 'a', function (err, fd) { ... }) anyway after a minute search try this :

var path = require('path'); 

path.exists('foo.txt', function(exists) { 
  if (exists) { 
    // do something 
  } 
}); 

// or 

if (path.existsSync('foo.txt')) { 
  // do something 
} 

For Node.js v0.12.x

Both path.exists and fs.exists have been depreciated

Using fs.stat:

fs.stat('foo.txt', function(err, stat) {
    if(err == null) {
        console.log('File exists');
    } else if(err.code == 'ENOENT') {
        fs.writeFile('log.txt', 'Some log\n');
    } else {
        console.log('Some other error: ', err.code);
    }
});

@Fox: great answer! Here's a bit of an extension with some more options. It's what I've been using lately as a go-to solution:

var fs = require('fs');

fs.lstat( targetPath, function (err, inodeStatus) {
  if (err) {

    // file does not exist-
    if (err.code === 'ENOENT' ) {
      console.log('No file or directory at',targetPath);
      return;
    }

    // miscellaneous error (e.g. permissions)
    console.error(err);
    return;
  }


  // Check if this is a file or directory
  var isDirectory = inodeStatus.isDirectory();


  // Get file size
  //
  // NOTE: this won't work recursively for directories-- see:
  // http://stackoverflow.com/a/7550430/486547
  //
  var sizeInBytes = inodeStatus.size;

  console.log(
    (isDirectory ? 'Folder' : 'File'),
    'at',targetPath,
    'is',sizeInBytes,'bytes.'
  );


}

P.S. check out fs-extra if you aren't already using it-- it's pretty sweet. https://github.com/jprichardson/node-fs-extra)

A easier way to do this synchronously.

if (fs.existsSync('/etc/file')) {
    console.log('Found file');
}

The API doc says how existsSync work:
Test whether or not the given path exists by checking with the file system.

in old days before sit down I always check if chair is there then I sit else I have an alternative plan like sit on a coach. Now node.js site suggest just go (no needs to check) and the answer looks like this:

    fs.readFile( '/foo.txt', function( err, data )
    {
      if(err) 
      {
        if( err.code === 'ENOENT' )
        {
            console.log( 'File Doesn\'t Exist' );
            return;
        }
        if( err.code === 'EACCES' )
        {
            console.log( 'No Permission' );
            return;
        }       
        console.log( 'Unknown Error' );
        return;
      }
      console.log( data );
    } );

code taken from http://fredkschott.com/post/2014/03/understanding-error-first-callbacks-in-node-js/ from March 2014, and slightly modified to fit computer. It checks for permission as well - remove permission for to test chmod a-r foo.txt