gistfile1.txt

// Example code by plato demonstrating fs and async
// Before running this: Create a file foo.txt in the same directory as this
// Additionally, run npm install async
var async = require('async');
var fs = require('fs');

handleimg = function(callback){
  var raft={}; // to float down the waterfall
  raft.meta = {size:50, name:"foo.txt"};
  async.waterfall(
  [ 
    function(next){
      // Check filesize
      if(raft.meta.size == 0){ //no file uploaded
        next('none', raft);
      } else if(raft.meta.size >= 5000000){ //5Mb
        next('toobig', raft);
      } else {
        next(null, raft);
      };
    },
    function(raft, next){
      // Check extension
      var tmp = raft.meta.name.match(/\.[^\.]*$/);
      if(tmp != null){
        var ext = tmp[0].toLowerCase();
      } else {
        var ext = null;
      };
      if(ext != '.jpg' 
      && ext != '.jpeg'
      && ext != '.png'
      && ext != '.bmp'
      && ext != '.tif'
      && ext != '.tiff'
      && ext != '.txt')
      { 
        next('extension', raft);
      } else {
        raft.ext = ext;
        next(null, raft);
      };
    },
    function(raft, next){
      // Rename and save uploaded file
      raft.timenow = new Date();
      raft.newdir = './bar/'
      raft.newfilename = 'bar.txt';
        
      console.log('Attempting to rename '+raft.meta.path
      +' to '+raft.newdir+raft.newfilename);
      // Rename has trouble if from and to paths are on different disks.
      fs.exists('./bar/', function(exists){
        if(exists){
          fs.rename(raft.meta.name, raft.newdir+raft.newfilename, function(err){
            if(!err){
              console.log('rename OK');
              next(null, raft);
            } else {
              console.log('rename fail');
              console.log(err);
              next('rename',raft);
            };
          });
        } else {
          fs.mkdir(raft.newdir, function(err){
            if(!err){
              console.log('mkdir OK');
              fs.rename(raft.meta.name, raft.newdir+raft.newfilename, function(err){
                if(!err){
                  console.log('rename2 OK');
                  next(null, raft);
                } else {
                  console.log('rename2 error:\n'+err);
                  next('rename',raft);
                };
              });
            } else {
              next('mkdir', raft);
            };
          });
        };
      });
    }, 
  ],
    function(err, raft){ // final waterfall callback
      if(!err){
        callback(null, raft);
      } else {
        console.log('Saving image failed, reason: '+err);
        callback(err);
      };
    }
  ); // end of async.waterfall
};

handleimg(function(err, raft){
  console.log('Final raft:'+JSON.stringify(raft,null,2));
});