async-madness.js

// npm install cli-prompt
var prompt = require('cli-prompt');
var fs = require('fs');

var files = [
  {path: './foo', src: 'foo'},
  {path: './bar', src: 'bar'}
];

saveFiles(files, function() {
  console.log('done');
});

function saveFiles(files, callback) {
  files.forEach(attemptSave);
  function attemptSave(file, index, arr) {
    fs.exists(file.path, function(exists) {
      if (exists) {
        prompt(file.path+' exists, overwrite? [y|n]', function(overwrite) {
          if (overwrite == 'y') save();
          maybeCallback();
        });
      } else {
        save();
        maybeCallback();
      }
    });
    function save() {
      console.log('-> saved file', file.path);
      fs.writeFile(file.src, maybeCallback);
    }
    function maybeCallback() {
      if (index == arr.length - 1) callback();
    }
  }
}

function saveFilesSync(files) {
  files.forEach(function(file) {
    if (fs.existsSync(file.path)) {
      if (prompt(file.path+' exists, overwrite? [y|n]') !== 'y') {
        return;
      };
    }
    fs.writeFileSync(file.path, file.src);
  });
}

Save this file and run it, you'll see the first time its great, but the second time when the files exists you get:

./foo exists, overwrite? [y|n]./bar exists, overwrite? [y|n]n

Is the async lib supposed to help me here somehow?

Yeah, you want to do those in order. Try async.each, it should help.

Alternately, write a function that calls itself with the next element, or a callback if there are no more elements. I usually use .pop and check xs.length for this kind of thing.

the sync version was added just for my sanity...

@jesusabdullah, I brought in async but then it only prompted once, I am begging for you to write the code for me up there.

@jesusabdullah to the rescue https://gist.github.com/jesusabdullah/7722499

I'm curious to know what confuses about this problem. I think it's important to understand why it's difficult.