Difference between Renderer and ElementRef in angular 2

Question

What is the difference between Renderer and ElementRef? In Angular both are used for DOM Manipulation. I am currently using ElementRef alone for writing Angular 2 directives. If I get more info about Renderer, I can use that in my future directives.

Rohrer

Answer 1

The Renderer is a class that is a partial abstraction over the DOM. Using the Renderer for manipulating the DOM doesn't break server-side rendering or Web Workers (where direct access to the DOM would break).

ElementRef is a class that can hold a reference to a DOM element. This is again an abstraction to not break in environments where the browsers DOM isn't actually available.

If ElementRef is injected to a component, the injected instance is a reference to the host element of the current component.

There are other ways to acquire an ElementRef instance like @ViewChild(), @ViewChildren(), @ContentChild(), @ContentChildren(). In this case ElementRef is a reference to the matching element(s) in the template or children.

Renderer and ElementRef are not "either this or that", but instead they have to be used together to get full platform abstraction.

Renderer acts on the DOM and ElementRef is a reference to an element in the DOM the Renderer acts on.

Singleness

I'm wondering why renderer methods require elementRef.nativeElement instead of working with elementRef like viewContainerRef. This seems to be a bit inconsistent. Any ideas? – Grassi

It looks inconsistent, but I think it isn't. In earlier beta versions renderer just took ElementRef but they changed it later. I think in platforms like Universal ElementRef.nativeElement doesn't actually refer to a DOM element. If you check angular.io/docs/ts/latest/api/core/index/ElementRef-class.html you'll see that nativeElement is of type any instead of HTMLElement – Mamiemamma

In earlier beta versions renderer just took ElementRef but they changed it later. - that's interesting, thanks. yeah, nativeElement can refer to platform specific elements, but passing elementRef instead of elementRef.nativeElement is still a higher abstraction and would work any way – Grassi

I don't remember seeing a reason mentioned why they changed it. – Mamiemamma

Just checked sources, existing renderer is depracated in the most recent versions. – Grassi

I think I saw something like that mentioned. I don't know yet what the alternative approach will be. – Mamiemamma

Answer 2

Do notice that you should refrain from using ElementHref as it flagged with a security risk.

Angular 2 Documentation:

"Permitting direct access to the DOM can make your application more vulnerable to XSS attacks. Carefully review any use of ElementRef in your code. For more detail, see the Security Guide."

"Use this API as the last resort when direct access to DOM is needed. Use templating and data-binding provided by Angular instead. Alternatively you take a look at Renderer which provides API that can safely be used even when direct access to native elements is not supported."

Farcical

Actually using ElementRef itself doesn't do any harm. The culprit is ElementRef.nativeElement. This is IMHO (I'm all but a security expert) only security relevant if user provided data is used to add to the DOM, right? – Mamiemamma