最佳实践与填坑的积累

1. 删除由Angular组件创建的Host HTML元素选择器

写一个remove-host 指令

//remove the host of avatar to be rendered as svg
@Directive({
    selector: '[remove-host]'
})
class RemoveHost {
    constructor(private el: ElementRef) {
    }
    //wait for the component to render completely
    ngOnInit() {
        var nativeElement: HTMLElement = this.el.nativeElement,
            parentElement: HTMLElement = nativeElement.parentElement;
        // move all children out of the element
        while (nativeElement.firstChild) {
            parentElement.insertBefore(nativeElement.firstChild, nativeElement);
        }
        // remove the empty element(the host)
        parentElement.removeChild(nativeElement);
    }
}

使用方式：
<avatar [name]="hero.name" remove-host></avatar>

来自stackoverflow

2.判断<ng-content>为空

Wrap ng-content in an HTML element like a div to get a local reference to it, then bind the ngIfexpression to ref.childNodes.length == 0:

template: `<div #ref><ng-content></ng-content></div> 
           <span *ngIf="ref.childNodes.length == 0">
              Display this if ng-content is empty!
           </span>`

来自stackoverflow