Revisiting last year's AnguarJS feed reader

Written by David on May 16, 2014

Updated gist: https://gist.github.com/davidchang/078d74c3bc68e40dd4a9

Updated demo: davidandsuzi.com/misc/feed-reader/v2.html

The first real project I did with Angular was documented a year ago in this blog post. It was a really simple app that illustrated the power and potential of Angular, but since I’ve been working in Angular for the past year, I recently revisited this article and noticed a handful of anti-patterns.

If you don’t go back and read that post, I don’t blame you. It’s long.

The gist of the original code was this:

  • There’s an input box for the feed URL
  • every 30 seconds or on submit, call a Google API to retrieve the RSS feed
  • functionality to toggle light/dark theme and mark items as read, no functionality to save items’ state of being read/unread

In retrospect, it was a pretty good starting introduction. I didn’t use a lot of Angular features - everything was in a single controller and I didn’t utilize anything of the real single page architecture. No routing, no service for the Google API call. I just didn’t need it. Here are some of the anti-patterns.

DOM Manipulation

The whole philosophy of Angular is that you shouldn’t exactly need jQuery. That’s why they implement their own fallback jqLite to handle basic querying/manipulation. (If there is DOM manipulation, it is convention to occur only in directive code.)

Originally, I had this at the bottom of my code:

$(function() {
    var $body = $('body');
    $('#toggleTheme').click(function() {
        $body.toggleClass('dark');
    });

    //and an interval check every 30 seconds for the RSS feed
});

And that controlled this toggleTheme element:

<button class="btn" id='toggleTheme'><span>Toggle Dark/Light Theme</span></button>

What I should have done:

<button class="btn" ng-click="darkTheme = !darkTheme"><span>Toggle Dark/Light Theme</span></button>

Which would set $scope.darkTheme to true. I want to see this scope value on my body element, which is currently one step above my ng-controller, so I could have set $rootScope.darkTheme = true, or what I should really do is move my ng-controller onto body and remove it from the div element it had been on. So this:

<body>
    <div ng-controller="RssFeedCtrl">

should become:

<body ng-class="{dark : darkTheme}" ng-controller="RssFeedCtrl">
    <div>

using that darkTheme scope variable.

Regarding the interval check to manually click the #update button, that should exist in the controller as well, and should utilize the $interval service provided by Angular.

$http.jsonp instead of $.ajax

To make the Google API call, I was using $.ajax. This is interesting, because it is an asynchronous action outside of Angular’s “digest cycle” - basically, once it happens, Angular has no idea that anything has changed (this concept will hopefully be eliminated by 2.0 with Object.observe). Since Angular didn’t know about it, $scope.updateModel had to manually call $scope.$apply to trigger the digest.

But if we use $http.jsonp (these Angular services typically wrap everything in $scope.$apply themselves), we won’t need to manually call $apply ourselves. And unit testing will be easier, if we were going to write unit tests (for the same testability reasons, we would want to use $interval above instead of the native setInterval).

By the way, we’d probably want to move that Google API call into its own service, but that’s a bit of overkill right now. But the main idea is that controllers themselves should be pretty thin (the final gist isn’t a good example of this), and recurring logic/code can typically be abstracted out elsewhere, into a service or parent controller.

Angular expressions

Some of the scope methods are one liners that do basic expressions - toggleShow that does article.show = !article.show, or markAsRead that does article.read = !article.read (which should be renamed to toggleRead).

Simple expressions like this can be done inline without having to introduce scope methods.

<span ng-click="markAsRead(article)">...</span>

would become

<span ng-click="article.read = !article.read">...</span>

Angular App Initialization

When I first looked at the code from a year ago, I was surprised it worked at all. Because Angular apps are conventionally started like this:

<html ng-app="feedReaderApp">
    ...
    <body ng-controller="RssFeedCtrl">

and then have JavaScript like this:

angular.module('feedReaderApp', [])
    .controller('RssFeedCtrl', [function() {}]);

This is a standard so that you can achieve some readable and organized modularity and not completely pollute your global scope. I’m surprised that the original source let me pass a global function in as the Angular controller… that is clearly an anti-pattern.

New Code

With all that in mind, here’s the updated gist for a feed reader with better practices in mind. Demo can be found here.

I made all of the improvements above and updated to a stabler version of Angular 1.2/deprecated dependency on jQuery.

In the current example, I’m using a HackerNews RSS feed where the content of each RSS item is some HTML. Right now, doing will not render the HTML. If you want to, and you can trust that you won’t XSS yourself, you’ll have to get around Angular’s new 1.2 security stuff by injecting a dependency on ngSanitize in your app (and including that script so it’s available):

angular.module('feedReaderApp', ['ngSanitize'])

and then binding via ng-bind-html

<div ng-show='article.show' class='content' ng-bind-html="article.content"></div>