Cordova File API Wrapper

fileStorage.js

/* modified from https://codingwithspike.wordpress.com/2014/12/29/using-deferreds-with-the-cordova-file-api/ */
/* requires rsvp.js */
/* tested and working in iOS and Android on latest Cordova (5.2.0) and File plugin (4.0.0) */
/* uses dataDirectory which is not synced to iCloud on iOS. You can replace each reference to syncedDataDirectory, but then you will need to set cordova.file.syncedDataDirectory = cordova.file.dataDirectory on Android to maintain compatibility */

window.fileStorage = {
  write: function (name, data) {

    var name_arr = name.split('/'); 
    var name_index = 0; 

    var promise = new RSVP.Promise(function(resolve, reject) { 

      var fail = function(msg, error) { 
        reject("Write failed on "+msg+", code: "+error.code); 
      }; 

      var gotFileSystem = function(fileSystem) { 

        if(name_arr.length > 1) { 
          fileSystem.getDirectory(name_arr[name_index], {create:true}, gotDirectory, fail.bind(null, 'gotFileSystem - getDirectory')); 
        }
        else { 
          fileSystem.getFile(name, { create: true, exclusive: false }, gotFileEntry, fail.bind(null, 'gotFileSystem - getFile')); 
        }
      }; 

      var gotDirectory = function(directory) { 
        name_index++; 
        if(name_index == (name_arr.length - 1)) { 
          directory.getFile(name_arr[name_index], {create:true, exclusive:false}, gotFileEntry, fail.bind(null, 'gotDirectory - getDirectory')); 
        }
        else { 
          directory.getDirectory(name_arr[name_index], {create:true}, gotDirectory, fail.bind(null, 'gotDirectory - getFile')); 
        }
      }; 

      var gotFileEntry = function(fileEntry) { 
        fileEntry.createWriter(gotFileWriter, fail.bind(null, 'createWriter')); 
      }; 

      var gotFileWriter = function(writer) { 
        writer.onwrite = function() { 
          resolve(); 
        }; 
        writer.onerror = fail.bind(null, 'gotFileWriter'); 
        writer.write(data); 
      }; 

      window.resolveLocalFileSystemURL(cordova.file.dataDirectory, gotFileSystem, fail.bind(null, 'requestFileSystem')); 
    }); 
    return promise;
  },
 
  read: function (name) {
    
    var promise = new RSVP.Promise(function(resolve, reject) { 
      var fail = function (msg, error) {
        reject("Read failed on "+msg+", code: "+error.code);
      };

      var gotFileEntry = function (fileEntry) {
        fileEntry.file(gotFile, fail.bind(null, 'gotFileEntry'));
      };

      var gotFile = function(file) { 
        reader = new FileReader(); 
        reader.onloadend = function(evt) { 
          data = evt.target.result; 
          resolve(data); 
        }; 
        reader.onerror = fail.bind(null, 'gotFile'); 
        reader.readAsText(file); 
      }; 

      window.resolveLocalFileSystemURL(cordova.file.dataDirectory + name, gotFileEntry, fail.bind(null, 'resolveLocalFileSystemURL')); 
    }); 
    return promise; 
  },
 
  removeFile: function (name) {
    
    var promise = new RSVP.Promise(function(resolve, reject) { 

      var fail = function (msg, error) {
        reject("Remove file failed on "+msg+", code: "+error.code);
      };
      var gotFileEntry = function (fileEntry) {
        fileEntry.remove(function() { 
          resolve(); 
        }, fail.bind(null, 'remove')); 
      };
      window.resolveLocalFileSystemURL(cordova.file.dataDirectory + name, gotFileEntry, fail.bind(null, 'resolveLocalFileSystemURL')); 
    }); 
    return promise; 
  }, 

  removeDirectory: function(name) { 

    var promise = new RSVP.Promise(function(resolve, reject) { 

      var fail = function(msg, error) { 
        reject("Remove directory failed on "+msg+", code: "+error.code); 
      }; 

      var gotDirectory = function(directory) { 
        directory.removeRecursively(function() { 
          resolve(); 
        }, fail.bind(null, 'removeRecursively')); 
      }; 

      window.resolveLocalFileSystemURL(cordova.file.dataDirectory + name, gotDirectory, fail.bind(null, 'resolveLocalFileSystemURL')); 

    }); 
    return promise; 

  }
};

Example usage:

1st example - writing to a text file, then reading the text back and displaying it

fileStorage.write('test/test.txt','Test File Text').then(function() { 
  fileStorage.read('test/test.txt').then(function(data) { 
    alert("File contains: "+data); 
  }, function(error) { 
    alert("File read failed, error: "+error);  
  }); 
}, function(error) { 
  alert("File write failed, error: "+error); 
}); 

2nd example - saving an image locally
in this case the image's SRC attribute is a Blob URL
notice the data I'm writing is of type "arraybuffer" (a type of bytearray)

var img = document.getElementById('my_img'); 
var xhr = new XMLHttpRequest(); 
xhr.open('GET',img.src,false); 
xhr.responseType = 'arraybuffer'; 
xhr.onload = function(e) { 
  if(this.status == 200) { 
    fileStorage.write('saved-images/my_img.jpg', this.response).then(function() { 
      alert('Image saved successfully'); 
    }, function(error) { 
      alert('Image was not saved, error: '+error); 
    }); 
  }
  else { 
    alert('Could not load image, error: '+this.responseText); 
  }
}; 
xhr.send();