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[Angular 2] ElementRef, @ViewChild & Renderer
ElementRef:
In Angular2 Doc, it suggest to "avoid" using ElementRef. It access DOM directly, can easily be attacked.
import {Component, OnInit, ViewChild, Renderer, ElementRef} from ‘@angular/core‘;@Component({ moduleId: module.id, selector: ‘widget-three‘, template: `<input type="text" #inputRef/>`})export class WidgetThree { constructor(private elm: ElementRef) { console.log("elm:", this.elm) }} 
If we log out the ElementRef, we can see, it refer to host element.
Renderer:
In the doc, it also suggest, if you want to change some dom prop, use Renderer instead. ElementRef can be just a reference to access native element object.
import { Directive, ElementRef, Input, Renderer } from ‘@angular/core‘;@Directive({ selector: ‘[myHighlight]‘ })export class HighlightDirective { constructor(el: ElementRef, renderer: Renderer) { renderer.setElementStyle(el.nativeElement, ‘backgroundColor‘, ‘yellow‘); }}This will set the host element background as yellow.
@ViewChild():
Access Child element by Ref or Class Object.
import {Component, OnInit, ViewChild, Renderer} from ‘@angular/core‘;@Component({ moduleId: module.id, selector: ‘widget-three‘, template: `<input type="text" #inputRef/>`})export class WidgetThree { @ViewChild(‘inputRef‘) input; constructor(private renderer: Renderer) { } ngAfterViewInit(){ this.renderer.invokeElementMethod( this.input.nativeElement, ‘focus‘, [] ); }}Here we have a ref "inputRef", we use ref to access input element.
‘invokeElementMethod‘ will call the ‘focus‘ method the the input nativeElement which should be:
this.input.nativeElement.focus()But the risk is on mobile it might have different method to focus on input, ‘invokeElementMethod‘ can safely help us to call the method .
[Angular 2] ElementRef, @ViewChild & Renderer