[Fuente: http://scotch.io/tutorials/javascript/single-page-apps-with-angularjs-routing-and-templating]
Overview
Single page apps are becoming increasingly popular. Sites that mimic the single page app behavior are able to provide the feel of a phone/tablet application. Angular helps to create applications like this easily.
Our Simple App
We’re just going to make a simple site with a home, about, and contact page. Angular is built for much more advanced applications than this, but this tutorial will show many of the concepts needed for those larger projects.
Goals
- Single page application
- No page refresh on page change
- Different data on each page
File Structure
- script.js <!-- stores all our angular code --> - index.html <!-- main layout --> - pages <!-- the pages that will be injected into the main layout --> ----- home.html ----- about.html ----- contact.html
HTML
This is the simple part. We’re using Bootstrap and Font Awesome. Open up your index.html file and we’ll add a simple layout with a navigation bar.
<!-- index.html -->
<!DOCTYPE html>
<html>
<head>
<!-- SCROLLS -->
<!-- load bootstrap and fontawesome via CDN -->
<link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css" />
<link rel="stylesheet" href="//netdna.bootstrapcdn.com/font-awesome/4.0.0/css/font-awesome.css" />
<!-- SPELLS -->
<!-- load jquery, bootstrap, and angular via CDN -->
<script src="//ajax.googleapis.com/ajax/libs/jquery/2.0.3/jquery.min.js"></script>
<script src="//netdna.bootstrapcdn.com/bootstrap/3.0.0/js/bootstrap.min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.0.8/angular.min.js"></script>
<script src="script.js"></script>
</head>
<body>
<!-- HEADER AND NAVBAR -->
<header>
<nav class="navbar navbar-default">
<div class="container">
<div class="navbar-header">
<a class="navbar-brand" href="/">Angular Routing Example</a>
</div>
<ul class="nav navbar-nav navbar-right">
<li><a href="#"><i class="fa fa-home"></i> Home</a></li>
<li><a href="#about"><i class="fa fa-shield"></i> About</a></li>
<li><a href="#contact"><i class="fa fa-comment"></i> Contact</a></li>
</ul>
</div>
</nav>
</header>
<!-- MAIN CONTENT AND INJECTED VIEWS -->
<div id="main">
<!-- angular templating -->
<!-- this is where content will be injected -->
</div>
<!-- FOOTER -->
<footer class="text-center">
View the tutorial on <a href="http://scotch.io/tutorials/angular-routing-and-templating-tutorial">Scotch.io</a>
</footer>
</body>
</html>
For linking to pages, we’ll use the #. We don’t want the browser to think we are actually travelling to about.html or contact.html.
Angular Application
Module and Controller
We’re going to setup our application. Let’s create the angular module and controller. Check out the docs for more information on each.
First, we have to create our module and controller in javascript. We will do that now in script.js.
// script.js
// create the module and name it scotchApp
var scotchApp = angular.module('scotchApp', []);
// create the controller and inject Angular's $scope
scotchApp.controller('mainController', function($scope) {
// create a message to display in our view
$scope.message = 'Everyone come and see how good I look!';
});
Let’s add the module and controller to our HTML so that Angular knows how to bootstrap our application. To test that everything is working, we will also show the $scope.message variable that we created.
<!-- index.html -->
<!DOCTYPE html>
<!-- define angular app -->
<html ng-app="scotchApp">
<head>
<!-- SCROLLS -->
<!-- load bootstrap and fontawesome via CDN -->
<link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css" />
<link rel="stylesheet" href="//netdna.bootstrapcdn.com/font-awesome/4.0.0/css/font-awesome.css" />
<!-- SPELLS -->
<!-- load jquery, bootstrap, and angular via CDN -->
<script src="//ajax.googleapis.com/ajax/libs/jquery/2.0.3/jquery.min.js"></script>
<script src="//netdna.bootstrapcdn.com/bootstrap/3.0.0/js/bootstrap.min.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/angularjs/1.2.10/angular.min.js"></script>
<script src="//ajax.googleapis.com/ajax/libs/angularjs/1.2.10/angular-route.js"></script>
<script src="script.js"></script>
</head>
<!-- define angular controller -->
<body ng-controller="mainController">
...
<!-- MAIN CONTENT AND INJECTED VIEWS -->
<div id="main">
{{ message }}
<!-- angular templating -->
<!-- this is where content will be injected -->
</div>Inside of our main div, we will now see the message that we created. Since we have our module and controller set up and we know that Angular is working properly, we will start working on using this layout to show the different pages.
Injecting Pages into the Main Layout
ng-view is an Angular directive that will include the template of the current route (/home, /about, or /contact) in the main layout file. In plain words, it takes the file we want based on the route and injects it into our main layout (index.html).
We will add the ng-view code to our site in the div#main to tell Angular where to place our rendered pages.
<!-- index.html -->
...
<!-- MAIN CONTENT AND INJECTED VIEWS -->
<div id="main">
<!-- angular templating -->
<!-- this is where content will be injected -->
<div ng-view></div>
</div>
...Configure Routes and Views
Since we are making a single page application and we don’t want any page refreshes, we’ll use Angular’s routing capabilities.
Let’s look in our Angular file and add to our application. We will be using $routeProvider in Angular to handle our routing. This way, Angular will handle all of the magic required to go get a new file and inject it into our layout.
AngularJS 1.2 and Routing The ngRoute module is no longer included in Angular after version 1.1.6. You will need to call the module and add it to the head of your document to use it. This tutorial has been updated for AngularJS 1.2
// script.js
// create the module and name it scotchApp
// also include ngRoute for all our routing needs
var scotchApp = angular.module('scotchApp', ['ngRoute']);
// configure our routes
scotchApp.config(function($routeProvider) {
$routeProvider
// route for the home page
.when('/', {
templateUrl : 'pages/home.html',
controller : 'mainController'
})
// route for the about page
.when('/about', {
templateUrl : 'pages/about.html',
controller : 'aboutController'
})
// route for the contact page
.when('/contact', {
templateUrl : 'pages/contact.html',
controller : 'contactController'
});
});
// create the controller and inject Angular's $scope
scotchApp.controller('mainController', function($scope) {
// create a message to display in our view
$scope.message = 'Everyone come and see how good I look!';
});
scotchApp.controller('aboutController', function($scope) {
$scope.message = 'Look! I am an about page.';
});
scotchApp.controller('contactController', function($scope) {
$scope.message = 'Contact us! JK. This is just a demo.';
});
Now we have defined our routes with $routeProvider. As you can see by the configuration, you can specify the route, the template file to use, and even a controller. This way, each part of our application will use its own view and Angular controller.
Our home page will pull the home.html file. About and contact will pull their respective files. Now if we view our app, and click through the navigation, our content will change just how we wanted.
To finish off this tutorial, we just need to define the pages that will be injected. We will also have them each display a message from its respectiive controller.
<!-- home.html --> <div class="jumbotron text-center"> <h1>Home Page</h1> <p>{{ message }}</p> </div><!-- about.html --> <div class="jumbotron text-center"> <h1>About Page</h1> <p>{{ message }}</p> </div><!-- contact.html --> <div class="jumbotron text-center"> <h1>Contact Page</h1> <p>{{ message }}</p> </div>
SEO on Single Page Apps
Ideally, this technique would be used for an application after a person has signed in. You wouldn’t really want those pages indexed since they are personalized to that specific user. For example, you wouldn’t want your Reader account, Facebook logged in pages, or Blog CMS pages indexed.
If you did want SEO for you application though, how does SEO work for applications/sites that get their pages built with Javascript? Search enginges have a difficult time processing these applications because the content is built dynamically by the browser and not visible to crawlers.
Making Your App SEO Friendly
Techniques to make Javascript single page applications SEO friendly require regular maintenance. According to the officialGoogle suggestions, you would create HTML snapshots. The basic overview of how it would work is that:
- A crawler would find a pretty URL (
http://scotch.io/seofriendly#key=value) - The crawler would then ask the server for the contents of this URL (in a special modified way)
- Web server returns content using an HTML snapshot
- HTML snapshot is processed by the crawler
- Search results then show the original URL
For more information on this process, be sure to look at Google’s AJAX Crawling and their guide on creating HTML snapshots.
Conclusion
This was a very simple tutorial on how to get Angular routing to work with a layout and separate views. Now you can go ahead and create larger single page applications. There is much more to learn with Angular and I’ll keep writing about different features along my learning journey of Angular.
If anyone has any suggestions for future Angular articles or different ways to do what we’ve just done here (there are so many ways to write the same thing, it can drive a person insane), sound off in the comments.