MV* and Local Storage

20 Jun 2013 | By Alex Young | Comments | Tags frameworks mv* localStorage

Most AngularJS and Backbone.js projects that I’ve worked on have persisted data to a remote API. What about those times when storing data in the browser is sufficient? Enterprising developers have added support for localStorage to some MVC frameworks, but before dropping one of these plugins or libraries into your project you need to know a little background about the API and its limitations.

Browser Support

If you’re already set on building a modern, single page web application, legacy browser support probably isn’t a huge deal. The Can I use Web Storage page shows most browsers we typically target are supported. It refers to “name/value pairs” because it’s talking about the localStorage API.

The localStorage API

If you’ve never used it before, then you can think of window.localStorage as a key/value store for strings. You can stick any JavaScript value you like in there, but a string will be returned on retrieval.

window.localStorage.setItem('age', 18);
window.localStorage.getItem('age');
// "18"

This means you should think carefully about what data you store. Aspirations of creating a browser-based Photoshop backed by localStorage isn’t architecturally sensible – it would be nice if binary data could be stored, but for now you’ll have to make do with strings.

The storage limit in most browsers is 5 MB, which probably doesn’t sound like much, but it’s actually 1000 times more than is supported by cookies.

AngularJS

There are examples of apps that use localStorage on the AngularJS blog. One that I downloaded and picked apart was FoodMe by Igor Minar. In FoodMe, Igor creates a localStorage service which basically just wraps window.localStorage so it can be loaded with dependency injection. The $scope is then watched, and a string version of a given record is dumped into localStorage using JSON.stringify:

foodMeApp.factory('customer', function($rootScope, localStorage) {
  var LOCAL_STORAGE_ID = 'fmCustomer';
  var customerString = localStorage[LOCAL_STORAGE_ID];

  var customer = customerString ? JSON.parse(customerString) : {
    name: undefined,
    address: undefined
  };

  $rootScope.$watch(function() { return customer; }, function() {
    localStorage[LOCAL_STORAGE_ID] = JSON.stringify(customer);
  }, true);

  return customer;
});

The record is loaded from localStorage, and serialised using JSON.parse and JSON.stringify. Notice that Igor has used the object-style API: localStorage.setItem(key, value) and localStorage[key] = value are equivalent.

Backbone.js

Jerome Gravel-Niquet created Backbone.localStorage (GitHub: jeromegn / Backbone.localStorage, License: MIT, bower: backbone.localStorage), which allows collections to store data with localStorage. It’s a drop-in solution – barely any configuration is required. All you need to do is add a localStorage property to your collection classes.

Backbone.localStorage has tests, and the author is still updating it. GitHub currently lists 31 contributors.

Knockout

This isn’t meant to be an exhaustive review of localStorage libraries, but I thought I’d also mention Knockout. knockout.localStorage (GitHub: jimrhoskins / knockout.localStorage) by Jim Hoskins makes ko.observable and ko.observableArray objects able to persist data to localStorage. You’ll need to specify a persist property which includes the key to store the observable’s data under.

It’s not quite as well-maintained or tested as Backbone.localStorage, but it does the job. There are some open pull requests that add things like AMD support.

Events

The Web Storage specification also defines a “storage” event. It fires when data changes, but you can’t stop it unlike other DOM events. This might make a more convenient bridge to data-binding frameworks.

Sync

If you’ve made an amazing single page app that persists data to localStorage, and you’re interested in adding a server-side API so users can save and sync data, what do you do? Well, step back and redefine the problem. Since localStorage is limited in size, why not use it like a caching layer? Your application could store data locally until a server is available, which suits a lot of use-cases, including mobile deployment. This is exactly what Backbone Caching Sync by Yiorgis Gozadinos does.

Cache

Another use people have found for localStorage is caching client-side assets. One example of this is basket.js by Addy Osmani.

Bing and Google Search make extensive use of localStorage for stashing SCRIPT blocks that are used on subsequent page views. None of the other top sites from my previous post use localStorage in this way. Are Bing and Google Search onto something? Yes, definitely.

Summary

If you need to persist data, localStorage can slot into data-binding and MVC/MVVC frameworks rather nicely. There are libraries out there, but with JSON.parse and JSON.stringify it’s trivial to store data. For applications with a server, then localStorage can be used as a temporary cache, which has the added benefit of helping support devices with intermittent network access.

Node Roundup: Node 0.10.12, grunt-micro, connect-prerenderer

19 Jun 2013 | By Alex Young | Comments | Tags node modules cluster grunt connect express
You can send in your Node projects for review through our contact form.

Node 0.10.12

Node 0.10.12 was released yesterday. This version updates v8 and npm, and has a fix for the net module.

One minor change that I liked was readline now supports CTRL-L for clearing the screen – that means Node’s command-line interface will do this as well. Before hitting CTRL-L did nothing, which wasn’t very intuitive if you’re used to using readline tools.

grunt-micro

If size is important to you, then you’ll like grunt-micro (GitHub: markdalgleish / grunt-micro, License: MIT, npm: grunt-micro) by Mark Dalgleish. This Grunt plugin ensures a script is smaller than a given size. Mark suggests this is useful for client-side authors that have size claims in their project documentation, but it could be useful for other things, like warning about asset sizes in mobile projects.

connect-prerenderer

connect-prerenderer (GitHub: dai-shi / connect-prerenderer, License: BSD, npm: connect-prerenderer) by Daishi Kato is middleware for pre-rendering content to support systems that don’t interact well with Ajax-heavy interfaces. This is ideal for improving the SEO of a site.

The author has paid special attention to AngularJS – the documentation includes some Angular client-side code that adds support for the module.

jQuery Roundup: Magnific Popup, blend.js

18 Jun 2013 | By Alex Young | Comments | Tags jquery plugins graphics images lightbox
Note: You can send your plugins and articles in for review through our contact form.

Magnific Popup

Magnific Popup

Magnific Popup (GitHub: dimsemenov / Magnific-Popup, License: MIT, jQuery: magnific-popup) by Dmitry Semenov is a responsive lightbox plugin that should work with mobile devices and also Zepto.js. It’s modular and has a build tool so you can generate a build that only includes the features you need. Sass is used for CSS, so you could easily customise the styles to suit your project.

Keyboard shortcuts are supported, the arrow keys and escape allow images to be navigated – see the gallery demo for an example of this.

A lot of the work is done by CSS, which means high DPI displays are supported:

Default controls are made with pure CSS, without external graphics. For the main image there is a built in way to provide appropriate source for different pixel density displays.

Content other than images is supported as well. The documentation has examples of using Magnific Popup with Google Maps and videos. For more information, see the Magnific documentation.

blend.js

blend.js (GitHub: qur2 / blend.js, License: MIT) by Aurélien Scoubeau applies effects to images using Canvas. The effects themselves are functions that receive pixels. Processing is applied to sections of the image in a two-dimensional grid.

Custom parameters can be passed to blending functions:

// Create some effects that will use additional arguments
var colorfx = blend.cfx(function(color, context) { return context; });
var anglefx = blend.pfx(function(angle, radius, pixels) { return pixels; });

blender.fx(colorfx, 'rgb(255, 123, 123)').fx(anglefx, [Math.PI, .25]);
blender.fx(colorfx, '#FFF', '#AAA', '#666', '#111');

// Null is used to skip zones
blender.fx(colorfx, '#FFF', null, null, '#111');

// Update the image
blender.update();

There are some bundled effects as well: desaturate, neutralize, vignette, and contrast. These can be found under blend.fx.

The author has included Mocha tests which can be ran in a browser here: blend.js/test.html.

Backbone Fetch Cache, Backbone.VirtualCollection, WTCSS

17 Jun 2013 | By Alex Young | Comments | Tags backbone.js plugins

Backbone Fetch Cache

Backbone Fetch Cache (GitHub: mrappleton / backbone-fetch-cache) by Andy Appleton caches Backbone’s collection and model fetch requests. Data is stored in localStorage to speed up rendering. This is useful for caching Ajax requests with APIs that don’t allow control over response cache headers.

The plugin supports preloading data with the prefill option which can be passed to fetch, and the author has included some Jasmine tests.

Backbone.VirtualCollection

Backbone.VirtualCollection (GitHub: p3drosola / Backbone.VirtualCollection, License: MIT, npm: backbone-virtual-collection) by Pedro Solá allows Backbone.Marionette’s CollectionViews and CompositeViews to be used with instances of Backbone.Collection. This allows collections to be projected and sorted.

This example is from the project’s documentation:

var virtual_collection = new Backbone.VirtualCollection(tasks_collection, function (task) {
  return task.get('user_id') == 13;
});

var view = new TaskListView({
  collection: virtual_collection
});

The project has Mocha tests and some details on its philosophy in the readme.

WTCSS

WTCSS

WTCSS (GitHub: benfoxall / wtcss, License: MIT) by Ben Foxall uses PhantomJS to analyse the CSS on a page, then attempts to visually indicate where each rule applies to using a Canvas overlay.

It looks impressive – there are demos on the project’s homepage, and I suspect it could form the basis for a more advanced CSS analysis and debugging tool.

Data.IO, CoffyScript, Circular Progress

14 Jun 2013 | By Alex Young | Comments | Tags browser libraries ES6 coffeescript Canvas

Data.IO

Data.IO (GitHub: scttnlsn / data.io, License: MIT, npm: data.io) by Scott Nelson is a library for bidirectional syncing over Socket.IO. It has server-side resources which encapsulate logic and persistence. Resources are stacks of composable middleware functions that sync client requests. The client-side component is comparatively lightweight – it’s lower-level than Backbone.js, so I suspect it could be used with any data binding library.

Data.IO allows you to keep core business logic on the server, while easily subscribing to data in the client. It’s a bit like Backbone.js and Express, but purpose-built for working with data syncing.

CoffyScript

CoffyScript (GitHub: loveencounterflow / coffy-script) by “loveencounterflow” is a port of CoffeeScript that adds support for yield from ES6:

If you have never programmed with iterators and generators, you may imagine as a ‘resumable return’ for starters. For the more technically oriented, ES6 defines generators as “First-class coroutines, represented as objects encapsulating suspended execution contexts (i.e., function activations).” Well, maybe ‘resumable return’ is not so bad after all.

# Using a star after the arrow 'licenses' the use of `yield` in the function body;
# it basically says: this is not an ordinary function, this is a generator function:
count = ->*
  yield 1
  yield 2
  yield 3

# Calling a generator function returns a generator:
counting_generator = count()

# Now that we have a generator, we can call one of its methods, `next`:
log counting_generator.next()   # prints: { value: 1, done: false }

# ...and we can go on doing so until the generator becomes exhausted:
log counting_generator.next()   # prints: { value: 2, done: false }
log counting_generator.next()   # prints: { value: 3, done: false }
log counting_generator.next()   # prints: { value: undefined, done: true }
log counting_generator.next()   # throws an error saying "Generator has already finished"

The documentation in the readme is thorough, and explores various aspects of working with yield. For example: How Not to Yield to Callback Hell: Serializing Control Flow.

Circular Progress

Circular Progress

Circular Progress (GitHub: neoziro / circular-progress, License: MIT, bower: circular-progress) by Greg Bergé is a progress widget with no dependencies. Given a Canvas element, it’ll show a circular representation of a process’s progress:

var progress = new CircularProgress({
  radius: 70,
  strokeStyle: 'black',
  lineCap: 'round',
  lineWidth: 4
});

document.body.appendChild(progress.el);
progress.update(40);

AngularJS: Iterators and Filters

13 Jun 2013 | By Alex Young | Comments | Tags angularjs angularfeeds mvc bower

AngularJS has a rich expression-based system for filtering and ordering data based on predicates. The orderBy filter can be used with the ng-repeat directive:

<ul>
  <li ng-repeat="item in stories | orderBy:predicate:date"><a href=""></a></li>
</ul>

Today we’re going to use orderBy inside a controller using dependency injection to organise multiple feeds into a river of news sorted by date.

Iterating in Controllers

Before sorting and displaying stories, we need to collect them into a suitable data structure. An array will suffice (app/scripts/controllers/main.js):

$scope.stories = [];

Next we need to append stories to this collection, but only if they haven’t already been added. Let’s use a function to encapsulate that away from fetching stories:

$scope.fetchFeed = function(feed) {
  feed.items = [];

  var apiUrl = "http://query.yahooapis.com/v1/public/yql?q=select%20*%20from%20xml%20where%20url%3D'";
  apiUrl += encodeURIComponent(feed.url);
  apiUrl += "'%20and%20itemPath%3D'feed.entry'&format=json&diagnostics=true&callback=JSON_CALLBACK";

  $http.jsonp(apiUrl).
    success(function(data) {
      if (data.query.results) {
        feed.items = data.query.results.entry;
      }
      addStories(feed.items);

The addStories function just needs to loop over each feed item to determine if it’s already been added to $scope.stories. The angular.forEach API in module ng is the perfect way to do this:

function addStories(stories) {
  var changed = false;
  angular.forEach(stories, function(story, key) {
    if (!storyInCollection(story)) {
      $scope.stories.push(story);
      changed = true;
    }
  });
}

As you can see, forEach accepts an array and a function to call for each item. The storyInCollection function now needs to loop over each existing story to see if it’s already been added. Figuring out which story is unique is easy because feeds have an id value:

function storyInCollection(story) {
  for (var i = 0; i < $scope.stories.length; i++) {
    if ($scope.stories[i].id === story.id) {
      return true;
    }
  }
  return false;
}

Storing Data

Now we’ve got a list of stories in our scope, we need to sort them by date just like a real feed reader. Whenever addStories changes the list of stories we should sort it. AngularJS doesn’t really have any fancy functional methods like map or some, which you can find in ECMAScript 5 anyway, but it does provide API access to the filtering and sorting modules that are typically used in templates.

To access this functionality you’ll need to load $filter:

angular.module('djsreaderApp')
  .controller('MainCtrl', function($scope, $http, $timeout, $filter) {

$filter will return a function that knows how to sort or filter arrays. That means you need to call it with the name of the desired method, then call the value returned with an array and an expression: $filter(filter)(array, expression). To add sorting to our feeds, call $filter()() and update the $scope.stories array:

// At the end of addStories
if (changed) {
  $scope.stories = $filter('orderBy')($scope.stories, 'date');
}

The only thing left to do is update the template in app/views/mail.html:

<ul>
  <li ng-repeat="item in stories"><a href=""></a></li>
</ul>

If you add multiple feeds using the app’s web interface you should see them combined into a river of news.

Conclusion

The river of news view

You can find this code in commit ff4d6a6.

Node Roundup: evilscan, pm2, connectr

12 Jun 2013 | By Alex Young | Comments | Tags node modules security network cluster express connect
You can send in your Node projects for review through our contact form.

evilscan

It’s finally here, TCP port scanning in Node! evilscan (GitHub: eviltik / evilscan, License: GPLv3, npm: evilscan) by Michel Soisson is a command-line tool, and has several interesting features, like control over the amount of concurrency, geolocation information, banner grabbing, and JSON output.

The author is focusing on connect scans, but is interested in adding SYN scans and UDP support. He’s looking for contributors, and the project includes tests written with Mocha and Chai, so you really have no excuse not to help out! I think it’s great to see well-tested security-related modules.

pm2

pm2

pm2 (GitHub: Unitech / pm2, License: MIT, npm: pm2) by Alexandre Strzelewicz is a command-line process manager for Node. It can be used to start a program as a cluster of processes, and then monitor the cluster’s health, monitor the server itself (CPU/RAM/etc.), keep processes alive, log exceptions, and throttle programs that stop too quickly.

It also has tests written with Mocha, documentation, and examples.

connectr

connectr (GitHub: olalonde / connectr, License: MIT, npm: connectr) by Olivier Lalonde is a wrapper for Connect that allows middleware to be inserted at arbitrary points in the stack. That means you can add middleware before existing middleware.

It has a simple API: the before and after methods insert new middleware relative to other middleware, and it’s also possible to add middleware to the top of the stack with first, or even based on an index.

jQuery Roundup: Go Flat!

11 Jun 2013 | By Alex Young | Comments | Tags jquery plugins jqueryui design
Note: You can send your plugins and articles in for review through our contact form.

Apple’s iOS 7 was announced yesterday, with a divisive flat-design-inspired interface. Some have called it out for having inconsistent icons, and others have praised it for exploring the z-axis.

Designmodo's Flat UI.

Flat design isn’t new to the web. A few months ago, Designmodo’s Flat UI burst onto the scene, grabbing a huge amount of attention on Hacker News and reddit. Bootstrap 3 also has a decidedly flat and minimal aesthetic.

jQuery Mobile Flat-UI Theme is based on Designmodo’s project, and brings some of these design conventions over to jQuery Mobile.

If you’re looking to really take a bite out of Apple’s iOS 7 design, the use of transparency effects might edge you closer to Jony Ive’s aesthetic. You could use something like Blur.js (GitHub: jakiestfu / Blur.js) to get a jQuery plugin API for transparency, or just write the relevant CSS by hand.

Although themes and plugins are useful, the focus of modern flat design seems to be on colours. Choosing a suitable palette can be difficult, but there are shortcuts. I liked Daniel Jalkut’s post on Adobe’s Kuler – the iPhone app can be used to generate colour palettes from the camera, which Daniel describes as “granting superpowers to users”.

For more inspiration, plenty of flat design gallery sites have started to spring up – fltdsgn.com is one that I’ve enjoyed flicking through.

As interesting as Apple, Google, and Microsoft’s recent shift to flat design has been, doesn’t it seem a little bit reminiscent of the past?

You can't get flatter than this! Source: Operating System Interface Design Between 1981-2009.

Easystar.js, Boolasync, Synchroscope

10 Jun 2013 | By Alex Young | Comments | Tags angularjs libraries node async

Easystar.js

easystar

Easystar.js (GitHub: prettymuchbryce / easystarjs, License: MIT) by Bryce Neal is an A* pathfinding API. Given a map of tiles, easystar will find a path through traversable tiles on the grid:

var easystar = new EasyStar.js();
var grid = [[0,0,1,0,0],
            [0,0,1,0,0],
            [0,0,1,0,0],
            [0,0,1,0,0],
            [0,0,0,0,0]];

easystar.setGrid(grid);
easystar.setAcceptableTiles([0]);

easystar.findPath(0, 0, 4, 0, function(path)) {
  if (path === null) {
    console.log('Path was not found.');
  } else {
    console.log('Path was found. The first Point is:', path[0]);
  }
});

easystar.setIterationsPerCalculation(1000); 
easystar.calculate()

The readme has a full breakdown of the methods used in this example, and installation instructions.

Boolasync

Boolasync (GitHub: olalonde / boolasync, License: MIT, npm: boolasync) by Olivier Lalonde is a module for composing logic using chained calls to asynchronous functions:

fn1.and(fn2).or(fn3).and(fn4.orNot(fn5).and(fn6)).eval(function(err, res) {
  if (err) return console.error(err);
  if (res) {
    console.log('The expression evaluated to true.');
  } else {
    console.log('The expression evaluated to false.');
  }
});

It supports optional “monkey patching” which adds boolean logic methods to Function.prototype. Olivier has included Mocha tests and a roadmap for future features.

synchroscope

synchroscope (GitHub: dtinth / synchroscope, License: MIT, npm: synchroscope) by Thai Pangsakulyanont allows the scope to be shared between multiple AngularJS clients. It works by sending data encoded using JSON.stringify over Socket.IO.

There’s a synchroscope instance running on Nodejitsu so you can try out examples using jsFiddle and similar services. The author has asked Nodejitsu for an open source drone but is currently waiting for a response. He’s got two demos running: AngularJS Todos and Tic Tac Toe Game.

The bundled server stores everything in-memory, so it doesn’t currently scale across multiple processes. I imagine the server could easily be modified to use a database or perhaps pub/sub.

On the client the API is surprisingly minimal – once the $ync dependency has been added, data can be shared from $scope by calling $ync($scope, keys, room). It seems like an idiomatic way to make real-time web applications with AngularJS.

AngularJS and SVG

07 Jun 2013 | By John Munsch | Comments | Tags angularjs svg tutorials guest-post

John Munsch is a professional software developer with over 26 years of experience. These days he's building modern web app front ends with AngularJS after a couple of years spent doing the same kind of work with Backbone.js, Underscore.js, and Handlebars.js.

For some reason odd reason everybody thinks he's a front end guy these days despite most of his career being spent in the Java, C++, and C world.

This article was originally published at johnmunsch.wordpress.com/.

I’ve long been a fan of using SVG (Scalable Vector Graphics) to do images that I can change easily on the fly. When I say “long been a fan” I mean that when I first started doing it I hand wrote some SVG as XML to show a donation bar we needed for GameDev.net and I had a program that would change the amount thus far donated on the bar and run it through an early version of the Java Batik library to spit out a JPEG file we could put on the website. It was crude, but it sure beat making a new graphic two or three times a day.

Years later things have gotten a lot easier. Modern browsers have advanced to the point where you can include an SVG image in the page as easily as referring to them in an img tag like so, <img src=”something.svg”/>, or just dumping some SVG code straight into the middle of the HTML for your page like this <svg>…lots of vector graphics…</svg>. And editing? Why would you edit by hand anymore when Adobe Illustrator can generate SVG files of your drawings for you, or if you have no budget for such nice tools, Inkscape does a pretty good job and costs nothing.

So it occurred to me the other day that it would be interesting to see if I could use AngularJS and its ability to rewrite HTML on the fly and combine that with SVG in the browser to rewrite SVG on the fly. The answer is, it not only works, it’s downright easy to do so. I’ve provided a couple of different examples to show just how easy it is to so.

Example 1: SVG with AngularJS Model Values

Getting an image to start with was pretty easy. I went to The Noun Project and grabbed an icon of the sun I liked. It was provided by an unknown author in this case. The icon came in SVG format so all I did with it in Inkscape was add a little color and some text that showed the temperature. Then I saved that as a “Plain SVG” file rather than an “Inkscape SVG” file. It might have worked as well with the latter but I didn’t want any surprises.

Editing an SVG icon.

I then popped over to an HTML file I had generated and imported it with an image link like this:

<img alt="" src="images/sunshine_plus_temp.svg" />

I then hand edited the SVG file and found where the text for the temperature and replaced it with an AngularJS model variable reference. So:

<tspan sodipodi:role="line" id="tspan4542" x="97.124313" y="52.063747">87°</tspan>

became:

<tspan sodipodi:role="line" id="tspan4542" x="97.124313" y="52.063747">°</tspan>

The <img> way of loading the SVG had to change because AngularJS wasn’t going to replace a variable inside an image for me. So I simply pasted the contents of the sunshine_plus_temp.svg right into the middle of a page already setup for AngularJS and put the temp variable into my $scope. It worked like a charm. With an input field tied to the model variable, as I typed, the SVG graphic was automatically updated with the new value.

My final touch was to externalize the SVG file. Nobody wants to edit an HTML file with half a dozen or more embedded lumps of SVG in there. It could quickly turn into an unreadable mess. And, as I already observed, <img> won’t work either. Ah, but AngularJS jumps to the fore again because it has it’s ng-include directive. All I had to do was this:

<span ng-include="'images/sunshine_plus_temp.svg'"></span>

and AngularJS was including the image where I needed it and binding the variable to the model for real-time update. Here’s the final version of the code I came up with for my first example, note the second set of quotes inside the ng-include to tell it not to interpret the string inside there, it’s just a string to use directly:

  <div>
    <p>Example 1: Text updated on the fly in an SVG graphic via AngularJS.</p>
    <span ng-include="'images/sunshine_plus_temp.svg'"></span>
  </div>
  <label>Temperature</label> <input type="text" ng-model="temp"/>

It’s worth noting that Inkscape is still perfectly capable of editing the SVG file even after the change I made and I guess I could have just made the change within Inkscape in the first place and never bothered opening up the file to manually change it with a text editor.

Editing an SVG icon that has been modified by AngularJS.

Example 2: Incorporating an Image

We don’t really need a second example here, the first one showed pretty much everything but I wanted to show how easily images incorporate into SVG and help you achieve results that would be much much harder to do with other techniques. In this example I took a slides icon by Diego Naive, from The Noun Project, overlaid an image on top of it, and then overlaid a glossy reflection on top of half the slide, just to show that the image is fully incorporated by the graphic and can easily be rotated, have graphics on top of it, underneath it, etc. Stuff that would require a lot of work to do with many other techniques.

Again, I tested it out and edited the final SVG file to add a variable reference, in this case to instead of the specific file reference that I had added with Inkscape. This time, I will say that it does not edit nearly as well in Inkscape after the edit because it doesn’t know where to find an image named ””. Within the Inkscape editor you just see an error box where the image should be. Not perfect, but not debilitating either.

Here’s a page with links to both examples and to the GitHub repository with all the code for both: http://johnmunsch.github.io/AngularJSExamples/

AngularJS: Form Validation

06 Jun 2013 | By Alex Young | Comments | Tags angularjs angularfeeds mvc bower

This week we’re going to look at form validation with AngularJS. Angular has several directives that support form field validation, and they’re based on the HTML5 form validators. You can specify that a field is required, a certain size, a certain type, and should match a given pattern.

URL Validation

Chrome's validation message

This tutorial series is about a feed reader, so it’s lucky that one of the standard HTML5 validators is for checking URLs. It can be used by adding the type="url" attribute to an input. Angular supports this through the input url directive. It takes various options, of which we’re interested in required and ng-model.

The ng-model directive allows the input to be linked to a model, but any Angular expression can be used. The form directive allows forms to be managed with Angular, and bound to controllers.

Just by adding a form and an input with type="url" will result in some basic validation support (in app/views/main.html):

<form name="newFeed">
  URL: <input size="80" name="url" ng-model="newFeed.url" type="url" required>
  <button ng-click="addFeed(newFeed)">Add Feed</button>
</form>

However, this won’t quite work with the controller code that I wrote in the previous parts because addFeed isn’t set up to check validation.

Checking Validation State

In a controller, a bound value can be interrogated for the validation status by checking the $valid property. The previous addFeed, in app/scripts/controllers/main.js, can be changed as follows:

$scope.addFeed = function(feed) {
  if (feed.$valid) {
    // Copy this feed instance and reset the URL in the form
    $scope.feeds.push(feed);
    $scope.newFeed.url = {};
  }
};

This should work, but it does one thing wrong: $scope.newFeed.url can’t be reset by assigning it to an object literal, because newFeed is now decorated with internal properties to support validation. Instead, copy the new object, and reset the values in newFeed:

$scope.addFeed = function(feed) {
  if (feed.$valid) {
    // Copy this feed instance and reset the URL in the form
    var newFeed = angular.copy(feed);
    $scope.feeds.push(newFeed);
    $scope.fetchFeed(newFeed);
    $scope.newFeed.url = '';
  }
};

Fighting with HTML5

We should probably add error messages that are cross-browser compatible. To do that, you can use the ng-show directive:

<form name="newFeed" novalidate>
  URL: <input size="80" name="url" ng-model="newFeed.url" type="url" required>
  <button ng-click="addFeed(newFeed)">Add Feed</button>
  <span class="error" ng-show="newFeed.$error.required">Required!</span>
  <span class="error" ng-show="newFeed.$error.url">Invalid URL format!</span>
</form>

The ngShow directive can conditionally show part of the DOM based on an Angular expression – in this case the validation results are checked. Incidentally, validation results can be found in the $error property fo the model.

Also notice that I added the novalidate attribute to the form; if you don’t do this HTML5 validations will still kick in, which causes confusing behaviour.

Disabling the Button

Another nice touch is to use ng-disabled to disable the button when an invalid URL has been entered. The ngDisabled directive takes an Angular expression, like the previous directives discussed here:

<form name="newFeed" novalidate>
  URL: <input size="80" name="url" ng-model="newFeed.url" type="url" required>
  <button ng-disabled="!newFeed.$valid" ng-click="addFeed(newFeed)">Add Feed</button>
  <span class="error" ng-show="newFeed.$error.required">Required!</span>
  <span class="error" ng-show="newFeed.$error.url">Invalid URL format!</span>
</form>

The difference here is I’ve used ! to negate the expression: !newFeed.$valid. Yes, it’s really that easy!

Conclusion

There’s more to expressions than simple model-based truth tests – you can do pretty much anything short of control flow statements. For more, see Angular Developer Guide, Expressions.

The latest commit for this project was 0dcc996.

Node Roundup: 0.8.24, 0.10.10, speakingurl, node-xmljson

05 Jun 2013 | By Alex Young | Comments | Tags node modules web urls xml json
You can send in your Node projects for review through our contact form.

Node 0.8.24 and 0.10.10

Node 0.8.24 and Node 0.10.10 have been released. The 0.8 (maintenance) release gets an updated npm, and some fixes for the url and http core modules.

Meanwhile, 0.10.10 has a new version of the internal uv library, and unshift('') now behaves like a noop.

speakingurl

Sascha Droste sent in speakingurl (GitHub: pid / speakingurl, License: BSD, npm: speakingurl), a module for generating clean URL slugs:

slug = getSlug('Apple & Pear!');
console.log(slug);
// Output: apple-and-pear

slug = getSlug('Foo ♥ Bar');
console.log(slug);
// Output: foo-love-bar

It has tests, localisation support, and works in browsers.

node-xmljson

node-xmljson (GitHub: ExactTarget / node-xmljson, License: MIT, npm: xmljson) from Adam Alexander and Benjamin Dean of ExactTarget was just released, providing quick and simple bi-directional translation between XML and JSON formats.

XML to JSON:
// Load the module
var to_json = require('xmljson').to_json;

// An XML string
var xml = '' +
    '<data>' +
        '<prop1>val1</prop1>' +
        '<prop2>val2</prop2>' +
        '<prop3>val3</prop3>' +
    '</data>';

to_json(xml, function (error, data) {
    // Module returns a JS object
    console.log(data);
    // -> { prop1: 'val1', prop2: 'val2', prop3: 'val3' }

    // Format as a JSON string
    console.log(JSON.stringify(data));
    // -> {"prop1":"val1","prop2":"val2","prop3":"val3"}
});
JSON to XML:
// Load the module
var to_xml = require('xmljson').to_xml;

// A JSON string
var json = '' +
    '{' +
        '"prop1":"val1",' +
        '"prop2":"val2",' +
        '"prop3":"val3"' +
    '}';

to_xml(json, function (error, xml) {
    // Module returns an XML string
    console.log(xml);
    // -> <data><prop1>val1</prop1><prop2>val2</prop2><prop3>val3</prop3></data>
});

ExactTarget has also released Fuel UX (GitHub: ExactTarget / fuelux, License: MIT) a lightweight web UI library that extends Twitter Bootstrap with additional JavaScript controls.

jQuery Roundup: 1.10.1, 2.0.2, ikSelect, photoWall.js

04 Jun 2013 | By Alex Young | Comments | Tags jquery plugins select galleries images
Note: You can send your plugins and articles in for review through our contact form.

jQuery 1.10.1 and 2.0.2

“A new release already? It’s only been a week! Yes, because you deserve it. We’re greatly encouraged by all the people who upgraded and found our well-hidden ‘we completely hosed relative animations’ easter egg,” writes Dave Methvin, about the release of jQuery 1.10.1 and 2.0.2.

The full background to this bug was documented in ticket #13939. Another animation-related bug was fixed, and an IE selector/iframe issue as well.

ikSelect

ikSelect (GitHub: Igor10k / ikSelect) by “Igor10k” is another select replacement plugin! This one supports custom markup and inline-block, optgroup, adding and removing options, callbacks, and event triggers.

The API is clean and idiomatic jQuery. There’s a single entry point, $(selector).ikSelect which can be used to apply the plugin to a select, or issue commands to an instance of ikSelect. Various options are supported, like setting the width automatically and adding search support (known as filtering in this case).

photoWall.js

photoWall.js (GitHub: jeremyjcpaul / photowall, License: MIT, jQuery: photowall) by Jeremy JC Paul creates a photo gallery in a similar style to Google+/Picasa, where clicking on an image opens a panel that displays additional metadata.

The markup allows the photo’s title and description to be specified like this:

<div class="photowall">
  <div class="pw-slide">
    <img class="pw-image" src="images/image-filename.jpg" />
    <div class="pw-image-desc">
      <!-- Any HTML content can go in here. -->
    </div>
  </div>
</div>

The plugin is invoked using $(selector).photoWall(), and supported options include event handlers and animation speed.

Angular Smart Table, TurtleScript

03 Jun 2013 | By Alex Young | Comments | Tags angular rust angularjs libraries education

Smart Table

Smart Table

Smart Table (GitHub: lorenzofox3 / Smart-Table, License: MIT) by Laurent Renard helps quickly render data as tables in AngularJS projects. It provides the smart-table directive which will render a rowCollection – an array that contains objects for each row. It also supports layouts by specifying the columns with columnCollection, data formatting, and sorting.

Smart Table has some more advanced features as well, like styling and inline editing. Laurent has included API documentation and unit tests.

TurtleScript

TurtleScript (GitHub: cscott / TurtleScript, License: GPLv2) by C. Scott Ananian from One Laptop per Child aims to provide a Logo-like environment for teaching programming. TurtleScript itself is based on JavaScript, and uses a bytecode compiler/interpreter.

The TurtleScript documentation has a lot more background that explains what it does and how it works. Meanwhile, Scott has been working on rusty-turtle (GitHub: cscott / rusty-turtle, License: GPLv2). This is a TurtleScript implementation written in Rust. If you’re interested in the Rust language and want to see what a JavaScript parser in Rust might look like, check it out!

Rusty-turtle is a “native” bytecode interpreter, so it runs the TurtleScript parser and compiler in order to generate bytecode for it to run.

Generators and Suspend

31 May 2013 | By Alex Young | Comments | Tags node modules es6

ECMAScript 6 generators are at the draft stage, and available in Node 0.11 when node is run with --harmony or --harmony-generators. Generators are “first-class coroutines” – think functions that can be postponed and resumed.

Generators are denoted with function*, and return values by calling yield. The value isn’t really returned: yield could be placed inside a loop, and then generator.next() is called to fetch the yielded value. The generator is said to be an iterator – it could be provided as the expression to an iteration statement like for:

function* generator() {
  for (;;) {
    yield someValue;
  }
}

for (var value of generator()) {
  // Do something with `value`,
  // then `break` when enough values have been yielded
}

The ECMAScript 6 wiki has a Fibonacci sequence example, but generators don’t really hit their conceptual stride until you start hooking generators up to other generators. The classic example of this is consumer-producer relationships: generators that produce values, and then consumers that use them. The two generators are said to be symmetric – a continuous evaluation where coroutines yield to each other, rather than two functions that call each other.

Jeremy Martin sent in a small but novel module based on generators called suspend (GitHub: jmar777 / suspend, License: MIT, npm: suspend). As it needs Node 0.11 and for Node to be run with --harmony, let’s just say it’s academically interesting for now.

You can think of suspend as an early example of generators that feature an idiomatic Node API:

// async without suspend
async.map(['file1','file2','file3'], fs.stat, function(err, results) {
  // results is now an array of stats for each file
});

// async with suspend
var res = yield async.map(['file1','file2','file3'], fs.stat, resume);

Here the async module has been modified to use suspend, resulting in more concise code.

suspend is “red light, green light” for asynchronous code execution. yield means stop, and resume means go.

If this sounds familiar, that’s because it’s not semantically too different to node-fibers. The node-fibers documentation includes a comparison between the ES6 generators example and its own syntax.

This is the entire source to suspend:

var suspend = module.exports = function suspend(generator, opts) {
  opts || (opts = {});

  return function start() {
    Array.prototype.unshift.call(arguments, function resume(err) {
      if (opts.throw) {
        if (err) return iterator.throw(err);
        iterator.send(Array.prototype.slice.call(arguments, 1));
      } else {
        iterator.send(Array.prototype.slice.call(arguments));
      }
    });
    var iterator = generator.apply(this, arguments);
    iterator.next();
  };
};

The suspend function accepts a generator and returns a function. The callback supplied to suspend will be passed the resume function, which accepts an error argument to fit Node’s callback API style. The user-supplied callback can then call yield on an asynchronous function that accepts resume as its callback, allowing Node’s core modules (or any other asynchronous methods) to be used in a synchronous style:

suspend(function* (resume) {
  var data = yield fs.readFile(__filename, resume);
})();

I liked this twist on generators, and I think modules like this will start to become more important in the JavaScript community over the next few years.

AngularJS: Adding Dependencies

30 May 2013 | By Alex Young | Comments | Tags angularjs mvc angularfeeds bower grunt

Adding Dependencies with Bower

This tutorial is really about Yeoman, Bower, and Grunt, because I still feel like it’s worth exploring the build system that I introduced for this AngularJS project. I appreciate that the number of files installed by Yeoman is a little bit bewildering, so we’re going to take a step back from AngularJS and look at how dependencies work and how to add new dependencies to a project.

Although Yeoman helps get a new project off the ground, it takes a fair amount of digging to figure out how everything is laid out. For example: let’s say we want to add sass-bootstrap to djsreader – how exactly do we do this?

Yeoman uses Bower for managing dependencies, and Bower uses component.json (or bower.json by default in newer versions). To add sass-bootstrap to the project, open component.json and add "sass-bootstrap": "2.3.x" to the dependencies property:

{
  "name": "djsreader",
  "version": "0.0.0",
  "dependencies": {
    "angular": "~1.0.5",
    "json3": "~3.2.4",
    "es5-shim": "~2.0.8",
    "angular-resource": "~1.0.5",
    "angular-cookies": "~1.0.5",
    "angular-sanitize": "~1.0.5",
    "sass-bootstrap": "2.3.x"
  },
  "devDependencies": {
    "angular-mocks": "~1.0.5",
    "angular-scenario": "~1.0.5"
  }
}

Next run bower install to install the dependencies to app/components. If you look inside app/components you should see sass-bootstrap in there.

Now the package is installed, how do we actually use it with our project? The easiest way is to create a suitable Grunt task.

Grunt

Grunt runs the djsreader development server and compiles production builds that can be dropped onto a web server. Gruntfile.js is mostly configuration – it has the various settings needed to drive Grunt tasks so they can build our project. One task is compass – if you search the file for compass you should see a property that defines some options for compiling Sass files.

The convention for Grunt task configuration is taskName: { argument: options }. We want to add a new argument to the compass task for building the Bootstrap Sass files. We know the files are in app/components/sass-bootstrap, so we just need to tell it to compile the files in there.

Add a new property to compass called bootstrap. It should be on line 143:

compass: {
  // options/dist/server
  bootstrap: {
    options: {
      sassDir: '<%= yeoman.app %>/components/sass-bootstrap/lib',
      cssDir: '.tmp/styles'
    }
  }
}

Near the bottom of the file add an entry for compass:bootstrap to grunt.registerTask('server', [ and grunt.registerTask('build', [:

grunt.registerTask('server', [
  'clean:server',
  'coffee:dist',
  'compass:server',
  'compass:bootstrap', /* This one! */
  'livereload-start',
  'connect:livereload',
  'open',
  'watch'
]);

This causes the Bootstrap .scss files to be compiled whenever a server is started.

Now open app/index.html and add styles/bootstrap.css:

<link rel="stylesheet" href="styles/bootstrap.css">
<link rel="stylesheet" href="styles/main.css">

Conclusion

Angular/Bootstrap

The settings files Yeoman created for us makes managing dependencies easy – there’s a world of cool things you can find with bower search and try out.

This week’s code is in commit 005d1be.

Node Roundup: 0.10.8, msfnode, vnc-over-gif

29 May 2013 | By Alex Young | Comments | Tags node modules security gif vnc
You can send in your Node projects for review through our contact form.

Node 0.10.8

Node 0.10.8 was released last week. v8, uv, and npm were all upgraded, and there are fixes and improvements to be found in the http, buffer, and crypto modules. This is the third stable release so far in May.

msfnode

Metasploit

msfnode (GitHub: eviltik / msfnode, License: GPL 3, npm: msfnode) by Michel Soisson is a Metasploit API client for Node. Metasploit is a hugely popular penetration testing framework. This module allows you to use Node to script Metasploit. The Metasploit API supports things like managing jobs, loading plugins, and interacting with open sessions to compromised systems.

The module provides a metasploitClient constructor, which can be passed an object that contains the Metasploit server’s details, including login and password. The client is event-based, and the project’s readme has an example of how to get a login token and make a request against a server.

vnc-over-gif

Andrey Sidorov sent in vnc-over-gif (GitHub: sidorares / vnc-over-gif, License: MIT, npm: vnc-over-gif), a VNC viewer that uses animated gifs as the data transport. It currently has no client-side JavaScript, so it acts purely as a means of viewing a VNC session. The author is interested in expanding it further with an Ajax-based UI. There’s a good background to the project in the vnc-over-gif FAQ.

Although it isn’t interactive, it’s a great hack – the code is currently only around 50 lines, which Andrey claims only took 30 minutes to write.

jQuery Roundup: 1.10.0, 2.0.1, AopJS, Backbone.Cache and Backbone.Cleanup

28 May 2013 | By Alex Young | Comments | Tags jquery plugins backbone.js aspect-oriented
Note: You can send your plugins and articles in for review through our contact form.

1.10.0 and 2.0.1

jQuery 1.10.0 and 2.0.1 were released last week:

Our main goal with these two releases is to synchronize the features and behavior of the 1.x and 2.x lines, as we pledged a year ago when jQuery 2.0 was announced. Going forward, we’ll try to keep the two in sync so that 1.11 and 2.1 are feature-equivalent for example.

Even though these newer jQuery releases have shed the legacy IE support baggage, there are still IE-specific fixes: IE9 focus of death.

AopJS

AopJS (GitHub: victorcastroamigo / aopjs, License: MIT, jQuery: aop) by Víctor Castro Amigo is a minimal aspect oriented library for JavaScript, with a jQuery plugin. It has a chainable API that can be used to define advice, with various types: before, after, afterReturning, afterThrowing, and around.

The author has included unit tests, and the readme has plenty of examples. The jQuery portion of the project doesn’t add any specific aspect-oriented enhancements to jQuery itself, it just binds to $.aop.aspect.

Backbone.Cache and Backbone.Cleanup

Naor Ye sent in some of his Backbone.js plugins. Backbone.Cache allows you to define a cache object that models and collections can use. You’ll need to make your models and collections inherit from the right classes: Backbone.CachedModel and Backbone.CachedCollection provide a cacheObject property that can be used to point to a suitable object to use as a cache.

Backbone.Cleanup offers parent classes for views and Backbone.Router to help you clean and reuse nested views. A method called markCurrentView is used to set the current view, so when the view is no longer active its cleanup method will be triggered.

Cytoscape.js

27 May 2013 | By Alex Young | Comments | Tags libraries node maths

Cytoscape

Cytoscape.js (GitHub: cytoscape / cytoscape.js, License: LGPL, npm: cytoscape), developed at the Donnelly Centre at the University of Toronto by Max Franz, is a graph library that works with Node and browsers. This library is for working with “graphs” in the mathematical sense – interconnected sets of nodes connected by edges.

The API uses lots of sensible JavaScript idioms: it’s event-based, functions return objects so calls can be chained, JSON definitions of elements can be used, and nodes can be selected with selectors that are modelled on CSS selectors and jQuery’s API. That means you can query a graph with something like this: cy.elements('node:locked, edge:selected').

Styling graphs is also handled in a natural manner:

Graph style and data should be separate, and the library should provide core functionality with extensions adding functionality on top of the library.

Max and several contributs have been working on the project for two years now, so it’s quite mature at this point. The project comes with detailed documentation, a build script, and a test suite written with QUnit.

Node Hosting with Modulus

25 May 2013 | By Alex Young | Comments | Tags node hosting

Modulus

Modulus.io is a new hosting platform dedicated to Node. Why “platform”? Well, Modulus provides a complete stack for web application development: MongoDB is used for the database and file storage, and WebSockets are supported out of the box. Applications running on the Modulus stack get metrics – requests are logged and analysed in real-time. Horizontal scaling is supported by running multiple instances of your application.

Pricing is determined by the number of instances (servos) that you run, and storage used. The Modulus pricing page has some sliders, allowing you to see how much it’ll cost to run your application per-month.

I asked Modulus about using different versions of Node Node, as Heroku supports 0.4 to 0.10. However, at the time of writing only Node 0.8.15 is supported. Ghuffran Ali from Modulus said that they’re working on supporting multiple Node versions as soon as Monday (27th May), so keep an eye on the Modulus blog for details on that.

It’s easy to get started with Modulus – there’s a sample project, plus you can sign in with GitHub so it doesn’t take too much effort to get a basic application running. They’re also offering $15 free credit, so you could run something more substantial there to see how everything works.

Modulus uses a web-based interface for managing projects that allows various settings to be changed, like environmental variables, and a global SSL redirect. There’s also a command-line client – if you sign in with GitHub make sure you use modulus login with -g so you can sign in with your GitHub account.

On a related note, IrisCouch has joined Nodejitsu. That means CouchDB and Redis are now both supported by Nodejitsu:

This means that our users will be able to deploy their applications and databases from the same set of tools all backed by node.js. If you’re an existing IrisCouch user you will be notified and given ample time to migrate your IrisCouch account into a Nodejitsu account.

It’s impressive to see so much innovation in the Node hosting/PaaS space!