background.js

/**
 * Listens for the app launching then creates the window
 *
 * @see http://developer.chrome.com/apps/app.window.html
 */

var dbName = 'todos-vanillajs';

function launch() {
  chrome.app.window.create('index.html', {
    id: 'main',
    bounds: { width: 620, height: 500 }
  });
}

function showNotification(storedData) {

  var openTodos = 0;

  if ( storedData[dbName].todos ) {
    storedData[dbName].todos.forEach(function(todo) {
      if ( !todo.completed ) {
        openTodos++;
      }
    });
  }

  if (openTodos>0) {
    // Now create the notification
    chrome.notifications.create('reminder', {
        type: 'basic',
        iconUrl: 'icon_128.png',
        title: 'Don\'t forget!',
        message: 'You have '+openTodos+' things to do. Wake up, dude!'
     }, function(notificationId) {})
  }
}

// When the user clicks on the notification, we want to open the To Do list
chrome.notifications.onClicked.addListener(function( notificationId ) {
  launch();
  chrome.notifications.clear(notificationId, function() {});
});

chrome.app.runtime.onLaunched.addListener(launch);

chrome.alarms.onAlarm.addListener(function( alarm ) {
  chrome.storage.local.get(dbName, showNotification);
});