LiveScriptでCallback Hellに挑む

input.coffee

# 本当はLiveScript(.ls)だが、シンタックスハイライトの都合で.coffee

# ファイルを読み込む
err, files <-! fs.readdir source
if err then return console.log 'Error finding files: ' + err

# ファイルリストを回す
filename, fileIndex <-! files.forEach
console.log filename

# ファイルサイズを取得
err, values  <-! gm source + filename .size
if err then return console.log 'Error identifying file size: ' + err
console.log filename + ' : ' + values
that = @
aspect = (values.width / values.height)

# widthリストを回す
width, widthIndex <-! widths.forEach
height = Match.round width / aspect
console.log 'resizing ' + filename + 'to ' + height + 'x' + height

# リサイズして
err <-! that.resize width, height .write destination + 'w' + width + '_' + filename
if err then return console.log('Error writing file: ' + err)

original.js

// reference of original code
// http://callbackhell.com/

fs.readdir(source, function(err, files) {
  if (err) {
    console.log('Error finding files: ' + err)
  } else {
    files.forEach(function(filename, fileIndex) {
      console.log(filename)
      gm(source + filename).size(function(err, values) {
        if (err) {
          console.log('Error identifying file size: ' + err)
        } else {
          console.log(filename + ' : ' + values)
          aspect = (values.width / values.height)
          widths.forEach(function(width, widthIndex) {
            height = Math.round(width / aspect)
            console.log('resizing ' + filename + 'to ' + height + 'x' + height)
            this.resize(width, height).write(destination + 'w' + width + '_' + filename, function(err) {
              if (err) console.log('Error writing file: ' + err)
            })
          }.bind(this))
        }
      })
    })
  }
})

output.js

// アウトプット
(function(){
  fs.readdir(source, function(err, files){
    if (err) {
      return console.log('Error finding files: ' + err);
    }
    files.forEach(function(filename, fileIndex){
      console.log(filename);
      gm(source + filename).size(function(err, values){
        var that, aspect;
        if (err) {
          return console.log('Error identifying file size: ' + err);
        }
        console.log(filename + ' : ' + values);
        that = this;
        aspect = values.width / values.height;
        widths.forEach(function(width, widthIndex){
          var height;
          height = Match.round(width / aspect);
          console.log('resizing ' + filename + 'to ' + height + 'x' + height);
          that.resize(width, height).write(destination + 'w' + width + '_' + filename, function(err){
            if (err) {
              return console.log('Error writing file: ' + err);
            }
          });
        });
      });
    });
  });
}).call(this);