Angular logo - httpMaking an HTTP get request with Angular is fairly simple. What may seem a bit different is the way that you handle the request. Instead of nested callbacks, you set up a subscription that can handle a stream of data.

It’s difficult to imagine an Angular application that does not make HTTP GET requests, because making network requests is at the very heart of any Angular application. It’s one of the basics. And for any front-end web developer, an HTTP GET request should be nothing new; it’s a simple one-way transaction. You simply request a remote resource such as a HTML file, CSS file or JavaScript file, and that resource is returned to you. Most front-end web developers will leverage a JavaScript library such as jQuery to make HTTP GET requests, rather than piecing together vanilla JavaScript which has to instantiate the XMLHttpRequest object. But while there is nothing wrong with this approach, it can result in boilerplate code and much of that code will become difficult to manage as it scales. So, most would agree that this should really be avoided.

Angular’s HTTP module provides a get method, and on a very high level, it provides similar functionality to the jQuery.get() method. The biggest difference between the jQuery.get() method and the Angular HTTP.get method, is in what each returns. While the jQuery.get() method returns a promise, the Angular HTTP.get method returns an observable. Important to note that this observable is markedly more sophisticated than a JavaScript promise. You subscribe to this observable, rather than passing a callback to it (as is the case with a promise). Significantly, as a subscriber of this observable, you are notified any time the data stream changes. For a closer look, take check out the examples that follow.

Example # 1

In Example # 1, we have our home component. We have imported RXJS components because we will need those in order to handle the HTTP get request. In this case, the real action happens in the ngOnInit method. This method is executed when the component is initialized, so we know that our code will be executed each time the user navigates to this route. Inside the ngOnInit method, we get ahold of the http service (i.e. this.http), and execute the get method, passing it the URL of the HTTP request we need to make. We then chain the map method to the result of this get request, returning JSON.

Next, we chain the subscribe method. Here we are setting up a subscription to this data. What this means is: whenever there is new data, we want to “know about it”. We pass an anonymous function to the subscribe method, and inside of that function, we can handle the new data. In this case, what we do is set this.destinations to the new data.  The reference: this.destinations  is the destinations property of our component. We use the “this” keyword because we are inside of a method, and the “this” keyword gives us access to the component. Setting this.destinations  to the streamed data will update the UI, which we will look at next.

Example # 2

In Example # 2, we have our Angular template. This is an unordered list. There are numerous destinations in our streamed JSON data, but we only create one list item. The reason for this is: we use the ngFor attribute to create a list item for every destination in the destinations array. In each iteration of this array, we reference the destination variable, and display the various properties of that object such as countryCode, nameduration and price. These values appear in the UI.

Video Example Code

If you want to download the example code, visit this Github page, and then follow the instructions:


Unlike the jQuery.get() method, Angular’s HTTP.get() method returns an observable (rather than a promise), and observables are more sophisticated than promises. We also know that when you subscribe to an observable, you are notified each time the data stream is updated. Another strength of the observable design pattern is that it allows for more than one party to subscribe to it, and these subscriptions can be cancelled at any time. Now while the syntax needed to set up an HTTP GET request in Angular is fairly simple, consuming observables might take a little getting used to. But it’s every bit worth the effort: observables are powerful.