Whenever your application grows beyond a single script with a few dozen lines, it gets harder and harder to manage without a good separation of roles among app components. One of the most common models for structuring a complex application, no matter what language, is the Model-View-Controller (MVC) and its variants, like Model-View-Presentation (MVP).
There are several frameworks to help apply MVC concepts to a Javascript application, and most of them, as long as they are CSP compliant, can be used in a Chrome App. In this lab, we'll add an MVC model using both pure JavaScript and the AngularJS framework. Most of the AngularJS code from this section was copied, with small changes, from the AngularJS Todo tutorial.
Note: Chrome Apps don't enforce any specific framework or programming style.
If using AngularJS, download the Angular script and save it as angular.min.js.
If using JavaScript, you will need to add a very simple controller with basic MVC functionalities: JavaScript controller.js
Change the AngularJS index.html or JavaScript index.html to use a simple sample:
<!doctype html>
<html ng-app ng-csp>
<head>
<script src="angular.min.js"></script>
<link rel="stylesheet" href="todo.css">
</head>
<body>
<h2>Todo</h2>
<div>
<ul>
<li>
{{todoText}}
</li>
</ul>
<input type="text" ng-model="todoText" size="30"
placeholder="type your todo here">
</div>
</body>
</html>
<!doctype html>
<html>
<head>
<link rel="stylesheet" href="todo.css">
</head>
<body>
<h2>Todo</h2>
<div>
<ul>
<li id="todoText">
</li>
</ul>
<input type="text" id="newTodo" size="30"
placeholder="type your todo here">
</div>
<script src="controller.js"></script>
</body>
</html>
Note: The ng-csp directive tells Angular to run in a "content security mode". You don't need this directive when using Angular v1.1.0+. We've included it here so that the sample works regardless of the Angular version in use.
AngularJS todo.css and JavaScript todo.css are the same:
body {
font-family: "Helvetica Neue",Helvetica,Arial,sans-serif;
}
ul {
list-style: none;
}
button, input[type=submit] {
background-color: #0074CC;
background-image: linear-gradient(top, #08C, #05C);
border-color: rgba(0, 0, 0, 0.1) rgba(0, 0, 0, 0.1) rgba(0, 0, 0, 0.25);
text-shadow: 0 -1px 0 rgba(0, 0, 0, 0.25);
color: white;
}
.done-true {
text-decoration: line-through;
color: grey;
}
Check the results by reloading the app: open the app, right-click and select Reload App.
The previous sample, although interesting, is not exactly useful. Let's transform it into a real Todo list, instead of a simple Todo item.
Whether using pure JavaScript or AngularJS, the controller manages the Todo list: AngularJS controller.js or JavaScript controller.js.
function TodoCtrl($scope) {
$scope.todos = [
{text:'learn angular', done:true},
{text:'build an angular Chrome packaged app', done:false}];
$scope.addTodo = function() {
$scope.todos.push({text:$scope.todoText, done:false});
$scope.todoText = '';
};
$scope.remaining = function() {
var count = 0;
angular.forEach($scope.todos, function(todo) {
count += todo.done ? 0 : 1;
});
return count;
};
$scope.archive = function() {
var oldTodos = $scope.todos;
$scope.todos = [];
angular.forEach(oldTodos, function(todo) {
if (!todo.done) $scope.todos.push(todo);
});
};
}
(function(exports) {
var nextId = 1;
var TodoModel = function() {
this.todos = {};
this.listeners = [];
}
TodoModel.prototype.clearTodos = function() {
this.todos = {};
this.notifyListeners('removed');
}
TodoModel.prototype.archiveDone = function() {
var oldTodos = this.todos;
this.todos={};
for (var id in oldTodos) {
if ( ! oldTodos[id].isDone ) {
this.todos[id] = oldTodos[id];
}
}
this.notifyListeners('archived');
}
TodoModel.prototype.setTodoState = function(id, isDone) {
if ( this.todos[id].isDone != isDone ) {
this.todos[id].isDone = isDone;
this.notifyListeners('stateChanged', id);
}
}
TodoModel.prototype.addTodo = function(text, isDone) {
var id = nextId++;
this.todos[id]={'id': id, 'text': text, 'isDone': isDone};
this.notifyListeners('added', id);
}
TodoModel.prototype.addListener = function(listener) {
this.listeners.push(listener);
}
TodoModel.prototype.notifyListeners = function(change, param) {
var this_ = this;
this.listeners.forEach(function(listener) {
listener(this_, change, param);
});
}
exports.TodoModel = TodoModel;
})(window);
window.addEventListener('DOMContentLoaded', function() {
var model = new TodoModel();
var form = document.querySelector('form');
var archive = document.getElementById('archive');
var list = document.getElementById('list');
var todoTemplate = document.querySelector('#templates > [data-name="list"]');
form.addEventListener('submit', function(e) {
var textEl = e.target.querySelector('input[type="text"]');
model.addTodo(textEl.value, false);
textEl.value=null;
e.preventDefault();
});
archive.addEventListener('click', function(e) {
model.archiveDone();
e.preventDefault();
});
model.addListener(function(model, changeType, param) {
if ( changeType === 'removed' || changeType === 'archived') {
redrawUI(model);
} else if ( changeType === 'added' ) {
drawTodo(model.todos[param], list);
} else if ( changeType === 'stateChanged') {
updateTodo(model.todos[param]);
}
updateCounters(model);
});
var redrawUI = function(model) {
list.innerHTML='';
for (var id in model.todos) {
drawTodo(model.todos[id], list);
}
};
var drawTodo = function(todoObj, container) {
var el = todoTemplate.cloneNode(true);
el.setAttribute('data-id', todoObj.id);
container.appendChild(el);
updateTodo(todoObj);
var checkbox = el.querySelector('input[type="checkbox"]');
checkbox.addEventListener('change', function(e) {
model.setTodoState(todoObj.id, e.target.checked);
});
}
var updateTodo = function(model) {
var todoElement = list.querySelector('li[data-id="'+model.id+'"]');
if (todoElement) {
var checkbox = todoElement.querySelector('input[type="checkbox"]');
var desc = todoElement.querySelector('span');
checkbox.checked = model.isDone;
desc.innerText = model.text;
desc.className = "done-"+model.isDone;
}
}
var updateCounters = function(model) {
var count = 0;
var notDone = 0;
for (var id in model.todos) {
count++;
if ( ! model.todos[id].isDone ) {
notDone ++;
}
}
document.getElementById('remaining').innerText = notDone;
document.getElementById('length').innerText = count;
}
updateCounters(model);
});
Change the AngularJS index.html or JavaScript index.html:
<html ng-app ng-csp>
<head>
<script src="angular.min.js"></script>
<script src="controller.js"></script>
<link rel="stylesheet" href="todo.css">
</head>
<body>
<h2>Todo</h2>
<div ng-controller="TodoCtrl">
<span>{{remaining()}} of {{todos.length}} remaining</span>
[ <a href="" ng-click="archive()">archive</a> ]
<ul>
<li ng-repeat="todo in todos">
<input type="checkbox" ng-model="todo.done">
<span class="done-{{todo.done}}">{{todo.text}}</span>
</li>
</ul>
<form ng-submit="addTodo()">
<input type="text" ng-model="todoText" size="30"
placeholder="add new todo here">
<input class="btn-primary" type="submit" value="add">
</form>
</div>
</body>
</html>
<!doctype html>
<html>
<head>
<link rel="stylesheet" href="todo.css">
</head>
<body>
<h2>Todo</h2>
<div>
<span><span id="remaining"></span> of <span id="length"></span> remaining</span>
[ <a href="" id="archive">archive</a> ]
<ul class="unstyled" id="list">
</ul>
<form>
<input type="text" size="30"
placeholder="add new todo here">
<input class="btn-primary" type="submit" value="add">
</form>
</div>
<!-- poor man's template -->
<div id="templates" style="display: none;">
<li data-name="list">
<input type="checkbox">
<span></span>
</li>
</div>
<script src="controller.js"></script>
</body>
</html>
Note how the data, stored in an array inside the controller, binds to the view and is automatically updated when it is changed by the controller.
Check the results by reloading the app: open the app, right-click and select Reload App.
Chrome Apps are offline first, so the recommended way to include third-party scripts is to download and package them inside your app.
You can use any framework you want, as long as it complies with Content Security Policies and other restrictions that Chrome Apps are enforced to follow.
MVC frameworks make your life easier. Use them, specially if you want to build a non-trivial application.
Build Apps with AngularJS tutorial
AngularJS Todo tutorial
In 4 - Save and Fetch Data, you will modify your Todo list app so that Todo items are saved.