在Angular2中操纵DOM的更好方法

Question

What's the better way of manipulating the DOM to change the background of a specific div, rather than using document.getElementById('id').style.backgroundImage .

I'm trying to change backgrounds as I change my Url, but the only way I could think and easy is using document.getElementById()

changeBg() {
 var urlPath = window.location.pathname.split('/');
  switch (urlPath[4]) {
    case "Refreshments%20North":
     document.getElementById('homeBg').style.backgroundImage = "url('./assets/imgs/spur-2.jpg')";
     break;
   ... more cases
    default:
     document.getElementById('homeBg').style.backgroundImage = "url('./assets/imgs/background.jpg')";
  }
}

I also tried Renderer dependency but how do I target homeBg using this?

this.renderer.setElementStyle(this.elRef.nativeElement, 'background-image', "url(./assets/imgs/spur-2.jpg)"); 

Template -- is basically just a div

<nav></nav>
<div id="homeBg"></div>

Edit -- Moved my changeBg() to my sharedService

public changeBg() {
var urlPath = window.location.pathname.split('/');
switch (urlPath[4]) {
  case "Refreshments%20North":
    this.homeBg = this.sanitizer.bypassSecurityTrustStyle("url('./assets/imgs/spur-2.jpg')");
    break;
  default:
    this.homeBg = this.sanitizer.bypassSecurityTrustStyle("url('./assets/imgs/background.jpg')");
  }
}

Calling changeBg() service in my profile component

ngOnInit() {
  this.sharedService.changeBg(); // is this correct?
}

Profile template -- like this gives me an error Cannot read property 'homeBg' of undefined

<div class="home" id="homeBg" [style.background-image]="changeBg?.homeBg"></div>

Change background with route.param.subscribe()

this.routeSub = this.route.params.subscribe(params => {
  this.sharedService.changeBg();
}

Answer 1

Using binding and directives is the preferred way in Angular2 instead of imperative DOM manipulation:

<div [style.background-image]="myService.homeBg"

You need to sanitize the URL for Angular to accept it. See In RC.1 some styles can't be added using binding syntax for more details.

changeBg() {
 var urlPath = window.location.pathname.split('/');
  switch (urlPath[4]) {
    case "Refreshments%20North":
     this.homeBg = this.sanitizer.bypassSecurityTrustStyle("url('./assets/imgs/spur-2.jpg')");
     break;
   ... more cases
    default:
     this.homeBg = this.sanitizer.bypassSecurityTrustStyle( "url('./assets/imgs/background.jpg')");
  }
}

See also How to add background-image using ngStyle (angular2)?

Answer 2

You can use template references and @ViewChild decorator:

template :

<div #myDiv id="homeBg"></div>

component :

class MyComponent implements AfterViewInit{
    @ViewChild("myDiv")
    elRef:ElementRef

    ngAfterViewInit(){
        this.renderer.setElementStyle(this.elRef.nativeElement, 'background-image', "url(./assets/imgs/spur-2.jpg)");
    }

}