An Angular 2 Primer

Angular 2 is the much anticipated latest release of the Angular platform maintained by a team of engineers over at Google. The first iteration of Angular (which we may refer to as Angular 1 or 1.X at times) was and has been very well received within the JavaScript community. Many saw it as an improvement on smaller single-page application libraries like Backbone.js and Knockout.js because it essentially did “more” for you. You got a lot of functionality out of the box with the result being that you had to write less boilerplate code than you would with using a more basic library. Directives allow you to define custom attributes for any element that you want and Angular also boasts other great features such as native data-binding, an AMD like module loading system, and services using a solid promise implementation for asynchronous data transfer. All of this and more comes pre-packaged within Angular and is coupled with a great community behind it, an abundance of resources, as well as great support from the team over at Google. Because of all this, it is not too surprising that many companies and organizations have turned to it as a solution for building their web and mobile applications.

If there were a few points of criticism of Angular as a framework, it usually surrounded a slightly steeper learning curve when compared to other libraries, and the observation that perhaps there was a little “too much magic” going on under the hood without the developer really fully understanding what is happening 100% in all circumstances. This is always a double-edged sword with a framework that gives you a lot of functionality out of the box. On one hand, it is great to have a system where writing a relatively small amount of code will give you a lot of dynamic features and functionality with minimal effort. On the other hand, this sometimes requires that you follow a very defined and specific pattern in the way that you structure your code and if you ever want to do something that is perhaps a bit unorthodox from the accepted way, it might not be so easy and a framework that is a bit more rigid when it comes to custom implementations not always desired — especially when those hard-to-track-down bugs surface at inopportune times. Like with so many things, there will always be pros and cons to any technology you encounter.

Nonetheless, the reception and response to Angular 1 was/is overall very positive. It was often paired with Node.js development using the web application framework Express.js and the NoSQL database MongoDB to create what was known as the MEAN stack (MongoDB, Express, Angular, Node.js). Many readers may be familiar with this and other technology paring acronyms (such as LAMP: Linux, Apache, MySQL, and PHP or Python). When certain groupings of technologies complement each other well and play together nicely, it always makes for a better development experience all around.

Angular 2 Announcement and Pushback

In the latter part of 2014 Google announced that they were developing Angular 2. Usually these sorts of announcements are met with are met with a lot of excitement. After all, who wouldn’t like a shiny new version of something that you already like. However there was one overarching dark cloud the loomed over the Angular 2 announcement that was met with a lot of frustration within the web development community: Angular 2 would be essentially a rewrite of the codebase and drastically different enough from Angular 1.X such that there would be no foreseeable upgrade path to move from Angular 1.X to Angular 2. This meant that existing applications in Angular 1.X would essentially have to be rewritten. On top of this, it was not immediately clear how long Angular 1.X would continue to be supported with new releases and bug fixes.

Naturally, of course, some developers were upset by this. Only time will tell what the full impact of this decision and approach will be. Nonetheless, we move forward towards the future regardless of how much of the past comes along with it. That’s what we are aiming to do in the following discussions and tutorials.

NOTE: At the time of this writing it is still not entirely clear whether any of this will change and the Angular team will put an upgrade path in place. Also note, at the time of this writing in mid-2015, Angular 2 is still in “developer preview.” This means that many of the concepts and code samples presented in this book are subject to change. I will do my best to keep up to date on the latest changes as they roll out, but please note that there might be some sensitivity involved with functionality between different versions of Angular 2 and its surrounding tools. If you encounter anything in this regard, please do not hesitate to contact me via the above channels.

Introduction to Angular 2

Angular 2 incorporates many modern features of the latest iterations of JavaScript and tools within the JavaScript community being released circa halfway through the second decade of the 21st century (2010 – 2020). This includes many syntactical and functional features of ECMAScript 6 — the latest iteration of JavaScript up from ECMAScript 5, Node.js based dependency management with npm , TypeScript — the type checking JavaScript utility syntax that has been built and maintained by Microsoft, and a number of others. In short, the fingerprints of many of the newest emerging technologies within the web development world during this window of time are present on the Angular 2 framework. Similar to those that have come before, each release of Angular 2 will attempt to be a more malleable and useful option for developers looking to solve the common problems that they all face.

So let’s look all of these pieces that are essential for developing an Angular 2 application…

Node.js

Angular 2 uses Node.js and more specifically npm for installation of the various dependencies it requires. Having been first published by Ryan Dahl in 2009, Node.js — the open source software that allows the common web language of JavaScript to run outside the browser — has absolutely grabbed ahold of imaginations in the world of technology in its first half-decade of life. The explosion of Node.js applications and the exponentially increasing number of published modules of npm, the repository where Node.js modules are stored, are a huge indicator of its success as a platform.

So be sure head over to the Node.js website and install it for your OS. You will definitely be needing it as we go along.

ECMAScript 6

Angular 2 uses many implementations found in ECMAScript 6, or ES6 for short. It would be beneficial to take a brief look at some of the new features found in this latest version of JavaScript up from ES5. For example, ECMAScript 6 implements a more syntactical conceptualization of classes in JavaScript. While JavaScript classes are not and never have been classes in the strictest technical sense as they are in the traditional object-oriented languages Java, C++, and C#, many JavaScript applications can still be written in a way that incorporates a very class-like implementation using functions, constructors and prototypal inheritance. For example, you will often see something the following in a JavaScript application (ES5):

// ES5
function Animal() {
    this.color = 'brown';
    this.size = 'medium';
    this.age = 1;
}
Animal.prototype.sound = function() {
    console.log('Grunt');
};
Animal.prototype.move = function() {
    console.log('Running');
};

var beast = new Animal();

Inheritance can even be implemented in this approach…

function Dog() {
    Animal.call(this);
}
Dog.prototype = new Animal();
Dog.prototype.constructor = Dog

var fido = new Dog();
fido.color // brown;

By calling the Animal function and passing in the Dog function as the context, and new instance of a Dog will get all of the properties and methods found on Animal. We then do a little bit of additional cleanup with some of the prototype to make sure that the pointers are pointing at the right place.

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