Building an HTML5 Text Editor with the FileSystem APIs

// Save a file in the FileSystem.
function saveFile(filename, content) {
  filesystem.root.getFile(filename, {create: true}, function(fileEntry) {

    fileEntry.createWriter(function(fileWriter) {

      fileWriter.onwriteend = function(e) {
        // Update the file browser.
        listFiles();

        // Clean out the form field.
        filenameInput.value = '';
        contentTextArea.value = '';

        // Show a saved message.
        messageBox.innerHTML = 'File saved!';
      };

      fileWriter.onerror = function(e) {
        console.log('Write error: ' + e.toString());
        alert('An error occurred and your file could not be saved!');
      };

      var contentBlob = new Blob([content], {type: 'text/plain'});

      fileWriter.write(contentBlob);

    }, errorHandler);

  }, errorHandler);
}

Great writeup on how to use Javascript’s Filesystem API

Building an HTML5 Text Editor with the FileSystem APIs →