How to correctly manipulate DOM with Angular

This article mainly introduces how to correctly operate DOM in Angular. It has a certain reference value. Now I share it with everyone. Friends in need can refer to it

I had no choice but to take over an old project. The previous one My brother uses a lot of JQuery to manipulate the DOM in the Angular project, which is really unsophisticated. So how to use Angular to manipulate DOM elegantly?

Get element

1. ElementRef --- A wrapper around a native element inside of a View.

　　在Inject ElementRef into the constructor of the component to get the package of the entire component element.

@Component({
  selector: 'app-test-page',
  templateUrl: './test-page.component.html',
  styleUrls: ['./test-page.component.scss']
})
export class TestPageComponent implements OnInit {

  constructor(    private el: ElementRef
  ) { }

  ngOnInit() {
  }

  getDomTest() {
    console.dir(this.el);
  }
｝

　 The nativeElement in ElementRef is the outermost DOM element of the component. Then through the native DOM positioning method, the specified selector element can be obtained.

  getDomTest() {
    console.dir(this.el.nativeElement.querySelector('.test-get-dom')); // 获取指定的子元素
  }

2. @viewChild() --- You can use ViewChild to get the first element or the directive matching the selector from the view DOM.

#@viewChild can get the specified element, and the specified method can be a local variable or component type;

// HTML
<p class="tip-test-wrapper">
　　　
    <button class="test-get-dom"  (click)="getDomTest()">测试获取DOM</button>
 </p>
　　<app-dialog></app-dialog>


// ts
import { DialogComponent } from &#39;./../../common/components/dialog/dialog.component&#39;;


@Component({
  selector: &#39;app-test-page&#39;,
  templateUrl: &#39;./test-page.component.html&#39;,
  styleUrls: [&#39;./test-page.component.scss&#39;]
})
export class TestPageComponent implements OnInit {
　 // 通过本地变量获取元素  可通过read来指定获取的元素类型
  @ViewChild(&#39;testdom&#39; , { read: ViewContainerRef }) viewcontainer: ViewContainerRef;
  @ViewChild(&#39;testdom&#39;) viewelement: ElementRef;

　 // 通过组件类型来获取
  @ViewChild(DialogComponent) viewcontent: DialogComponent;

  constructor(
    private el: ElementRef
  ) { }

  ngOnInit() {
  }

  getDomTest() {
    // console.dir(this.el.nativeElement.querySelector(&#39;.test-get-dom&#39;));
    console.dir(this.viewcontainer);
    console.dir(this.viewelement);
    console.dir(this.viewcontent);
  }
}

　

Remarks: ElementRef or @ viewChild obtains elements and must be used after the ngAfterViewInit cycle.

3. @viewChildren -- You can use ViewChildren to get the {@link QueryList} of elements or directives from the view DOM.

@viewChild will return the first element that meets the conditions elements, what if you need to obtain multiple elements that meet the conditions?

@viewChildren will return a list of all elements that meet the conditions.

The method of specifying the selector is consistent with @viewChild.

// 复制一个元素
  <p class="tip-test-wrapper">
    <button class="test-get-dom" #testdom (click)="getDomTest()">测试获取DOM</button>
  </p>
  <p class="tip-test-wrapper">
    <button class="test-get-dom" #testdom (click)="getDomTest()">测试获取DOM</button>
  </p>
</p>
<app-dialog></app-dialog>
<app-dialog></app-dialog>// tsimport { DialogComponent } from &#39;./../../common/components/dialog/dialog.component&#39;;


@Component({
  selector: &#39;app-test-page&#39;,
  templateUrl: &#39;./test-page.component.html&#39;,
  styleUrls: [&#39;./test-page.component.scss&#39;]
})
export class TestPageComponent implements OnInit {

  @ViewChild(&#39;testdom&#39; , { read: ViewContainerRef }) viewcontainer: ViewContainerRef;
  @ViewChild(&#39;testdom&#39;) viewelement: ElementRef;  @ViewChildren(&#39;testdom&#39;) viewelements: QueryList<any>;

  @ViewChild(DialogComponent) viewcontent: DialogComponent;  @ViewChildren(DialogComponent) viewcontents: QueryList<DialogComponent>;

  constructor(    private el: ElementRef
  ) { }

  ngOnInit() {
  }

  getDomTest() {    // console.dir(this.el.nativeElement.querySelector(&#39;.test-get-dom&#39;));    // console.dir(this.viewcontainer);
    console.dir(this.viewelement);
    console.dir(this.viewelements);
    console.dir(this.viewcontent);
    console.dir(this.viewcontents);
  }

Operation DOM --- Renderer2

After obtaining the dom, how to operate the dom? The native domAPI is an option, but Angular provides a better cross-platform way Renderer2.

Introduction

Renderer2 ,

Then inject it in construct.

import { Component, OnInit , ViewContainerRef , ElementRef , ViewChild,  , ViewChildren, QueryList} from '@angular/core';

import { DialogComponent } from './../../common/components/dialog/dialog.component';


@Component({
  selector: 'app-test-page',
  templateUrl: './test-page.component.html',
  styleUrls: ['./test-page.component.scss']
})
export class TestPageComponent implements OnInit {

  @ViewChild('testdom' , { read: ViewContainerRef }) viewcontainer: ViewContainerRef;
  @ViewChild('testdom') viewelement: ElementRef;
  @ViewChildren(&#39;testdom&#39;) viewelements: QueryList<any>;
  @ViewChild(DialogComponent) viewcontent: DialogComponent;
  @ViewChildren(DialogComponent) viewcontents: QueryList<DialogComponent>;

  constructor(
    private el: ElementRef
  ) { }

  ngOnInit() {
  }

  getDomTest() {

    
  }
｝

　renderer2 provides a rich API for use

, as follows:

Summary

Through elementRef or @ viewChild @viewChildren gets the element, and then operates the element through the API provided by renderer2. But remember not to use it before the ngAfterViewInit cycle. Through the methods provided by Angular, most of the needs for operating DOM can be met. If there is a special scene, of course it is better to use the native DOM.

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