FileSystem API write and read text

FileSystemAPITest

(function (window, document, undefined) {

    'use strict';

    window.FS = window.FS || (function () {

        //use fallback if fileSystem is prefixed in specifc UA
        window.requestFileSystem = window.requestFileSystem || window.webkitRequestFileSystem;

        var saveTextFile = function (fileName, value, saveCompleteCallback) {

            //request the FileSystem, use callback on success (error cb is optional)
            //@see https://developer.mozilla.org/en-US/docs/Web/API/LocalFileSystem
            window.requestFileSystem('PERSISTENT', 1024, function (fileSystem) {

                //The DirectoryEntry at the root of the fs
                var root = fileSystem.root;

                root.getMetadata(function (metaData) {
                    console.log("save: metadata of file", fileName, metaData);
                });

                //use the DirectoryEntry at the root to lookup or create a file, use callback when complete
                //add optional error-callback
                root.getFile(fileName, {create: true}, function (f) {

                    //we can use this FileEntry to create a writer
                    //@see https://developer.mozilla.org/en-US/docs/Web/API/FileEntry
                    //add optional error-callback
                    f.createWriter(function (fileWriter) {

                        fileWriter.onwriteend = function(e) {
                            if (saveCompleteCallback) {
                                saveCompleteCallback("success", e);
                            }
                        };

                        fileWriter.onerror = function(e) {
                            if (saveCompleteCallback) {
                                saveCompleteCallback("failed", e);
                            }
                        };

                        //Blob @see https://developer.mozilla.org/en-US/docs/Web/API/Blob
                        //modern browser desktop support
                        var s = new Blob([value], {type: 'text/plain'});
                        fileWriter.write(s);
                    });
                });
            });
        };

        var loadTextFile = function(fileName, onFileLoaded) {

            window.requestFileSystem('PERSISTENT', 1024, function(fs) {

                //The DirectoryEntry at the root of the fs
                var root = fs.root;

                //get fileEntry for the fileName
                //@see https://developer.mozilla.org/en-US/docs/Web/API/FileEntry
                root.getFile(fileName, {create: false}, function(fileEntry) {

                    fileEntry.file(function(file) {

                        //@see https://developer.mozilla.org/en-US/docs/Web/API/FileReader
                        var fileReader = new FileReader();

                        fileReader.onloadend = function(e) {
                            console.log("file content: ", this.result);
                            if (onFileLoaded) {
                                onFileLoaded(this.result);
                            }
                        };

                        fileReader.onerror = function(error) {
                            console.log("error reading file", fileName, error.message);
                        }

                        fileReader.readAsText(file);
                    });

                    fileEntry.getMetadata (function (metaData) {
                       console.log("load: metadata of file", fileName, metaData);
                    });

                }, function(error) {
                    console.log("error getting the file", fileName, error.message);
                });
            });
        };

        return {
            saveTextFile: saveTextFile,
            loadTextFile: loadTextFile
        };

    }());

}(window, document));

var loadTestFile = function (status, obj) {
    FS.loadTextFile('testFile');
};

FS.saveTextFile('testFile', 'Hello FileSystem', loadTestFile);