Angular 2 app: "XMLHttpRequest cannot load localhost endpoint" - rest

Question

I have my Angular front-end set up to try and hit a RESTful endpoint. The Angular front-end is being served on localhost:3000, and the RESTful back-end is being hosted on localhost:8080.
In my Angular rest client service, I make the call (which I subscribe to elsewhere in my application):
getCurrentSlides(): Observable<Slide[]> {
return this.http.get("localhost:8080/app/slides")
.map(extractData)
.catch(handleError);
}
But when Angular tries to hit that URL, I get the following error:
XMLHttpRequest cannot load localhost:8080/app/slides. Cross origin requests are only supported for protocol schemes: http, data, chrome, chrome-extension, https.
And yes, CORS is enabled on my server.

Answer 1

this.http.get("localhost:8080/app/slides")
You're missing the http:// in the URL. With that, most browsers will still require CORS for the different ports, but IE does not, so when adding http:// you should be able to test using IE:
IE Exceptions
Internet Explorer has two major exceptions when it comes to same origin policy
Trust Zones: if both domains are in highly trusted zone e.g, corporate domains, then the same origin limitations are not applied
Port: IE doesn't include port into Same Origin components, therefore http://company.com:81/index.html and http://company.com/index.html are considered from same origin and no restrictions are applied.
These exceptions are non-standard and not supported in any other browser but would be helpful if developing an app for Windows RT (or) IE based web application.
That said, you should enable CORS. (But it seems you did, so then it's just the missing http:// prefix.)