Home>Article>Web Front-end> Angular development practice (7): Cross-platform operation of DOM and renderer Renderer2
In"Angular Development Practice (6): Server-side Rendering"At the end of this article, we also mentioned several events that need to be kept in mind inServer-side rendering, These include not using browser-specific types such aswindow,document,navigatorand directly manipulating DOM elements.
This brings us to one of Angular’s main features: across all platforms. With the right approach, applications built using Angular can be reused on multiple different platforms - web, mobile web, mobile apps, native apps, and desktop native apps.
In order to support cross-platform, Angular encapsulates the differences of different platforms through abstraction layers. For example, abstract class Renderer2, abstract class RootRenderer, etc. are defined. In addition, the following reference types are defined: ElementRef, TemplateRef, ViewRef, ComponentRef, ViewContainerRef, etc. Obtain DOM elements throughtemplate variables,@ViewChildand other methods.
For demonstration, first define a component DemoComponent:
import { AfterViewInit, Component, ElementRef, Renderer2, ViewChild } from '@angular/core'; @Component({ template: ` this is p!
p的id：{{demop.id}} ` }) export class DemoComponent implements AfterViewInit { @ViewChild('demop') demop: ElementRef; // @ViewChild通过模板变量名获取 constructor(private renderer: Renderer2) { } ngAfterViewInit() { console.log('p的id：' + this.demop.nativeElement.id); // p的id：demop this.renderer.setStyle(this.demop.nativeElement, 'background-color', 'red'); // 通过Renderer2设置p的css样式background-color } }
In Angular applications, DOM elements should not be obtained directly through native API or jQuery:
let element1 = document.getElementById("demop"); // jQuery获取: $('#demop')
Instead, you should get the DOM element through the method provided by Angular:
a728b34f8c39ac4b8264402fa7a79be6this is p!94b3e26ee717c64999d7867364b1b4a3 p的id：{{demop.id}} 56a354faacebef689e1d2dd71ed7d1a6
In the component template, we define the template of #demop on p variable, then demop is equal to the DOM object of p, so we can directly obtain the id of p throughdemop.id.
@ViewChild('demop') demop: ElementRef; // @ViewChild通过模板变量名获取 ngAfterViewInit() { console.log('p的id：' + this.demop.nativeElement.id); // p的id：demop }
In the component class, we obtain the ElementRef object that wraps the DOM object of p through @ViewChild. The ElementRef is defined as follows:
class ElementRef8742468051c85b06f0a0af9e3e506b5c { constructor(nativeElement: T) nativeElement: T }
So we can Get the DOM object of p through this.demop.nativeElement in ngAfterViewInit, and then get the id of the element.
has obtained the DOM object of p through several methods above, so how do we operate on it (setting styles, attributes, inserting sub-elements, etc.) ? Via raw API or jQuery is definitely not allowed.
In this way, we introduce the Angular abstract classRenderer2to set styles, attributes, insert sub-elements and other operations on elements.
Renderer2 is defined as follows:
class Renderer2 { get data: {...} destroyNode: ((node: any) => void) | null destroy(): void createElement(name: string, namespace?: string | null): any // 创建元素 createComment(value: string): any // 创建注释元素 createText(value: string): any // 创建文本元素 appendChild(parent: any, newChild: any): void // 添加子元素（在最后） insertBefore(parent: any, newChild: any, refChild: any): void // 添加子元素（在最前） removeChild(parent: any, oldChild: any): void // 移除子元素 selectRootElement(selectorOrNode: string | any): any // 获取根元素 parentNode(node: any): any // 获取父元素 nextSibling(node: any): any // 获取下一个兄弟元素 setAttribute(el: any, name: string, value: string, namespace?: string | null): void // 设置属性 removeAttribute(el: any, name: string, namespace?: string | null): void // 移除属性 addClass(el: any, name: string): void // 添加样式类 removeClass(el: any, name: string): void // 移除样式类 setStyle(el: any, style: string, value: any, flags?: RendererStyleFlags2): void // 设置样式 removeStyle(el: any, style: string, flags?: RendererStyleFlags2): void // 移除样式 setProperty(el: any, name: string, value: any): void // 设置DOM对象属性，不同于元素属性 setValue(node: any, value: string): void // 设置元素值 listen(target: 'window' | 'document' | 'body' | any, eventName: string, callback: (event: any) => boolean | void): () => void // 注册事件 }
Therefore, if we want to change the background color of p, we can do this:
ngAfterViewInit() { this.renderer.setStyle(this.demop.nativeElement, 'background-color', 'red'); // 通过Renderer2设置p的css样式background-color }
At the end of the article "Angular Development Practice (6): Server-side Rendering", we also mentioned the need forServer-side renderingA few things to keep in mind include not using browser-specific types such aswindow,document,navigator, and directly manipulating DOM elements.
This brings us to one of Angular’s main features: across all platforms. With the right approach, applications built using Angular can be reused on multiple different platforms - web, mobile web, mobile apps, native apps, and desktop native apps.
In order to support cross-platform, Angular encapsulates the differences of different platforms through abstraction layers. For example, abstract class Renderer2, abstract class RootRenderer, etc. are defined. In addition, the following reference types are defined: ElementRef, TemplateRef, ViewRef, ComponentRef, ViewContainerRef, etc. Obtain DOM elements throughtemplate variables,@ViewChildand other methods.
For demonstration, first define a component DemoComponent:
import { AfterViewInit, Component, ElementRef, Renderer2, ViewChild } from '@angular/core'; @Component({ template: ` this is p!
p的id：{{demop.id}} ` }) export class DemoComponent implements AfterViewInit { @ViewChild('demop') demop: ElementRef; // @ViewChild通过模板变量名获取 constructor(private renderer: Renderer2) { } ngAfterViewInit() { console.log('p的id：' + this.demop.nativeElement.id); // p的id：demop this.renderer.setStyle(this.demop.nativeElement, 'background-color', 'red'); // 通过Renderer2设置p的css样式background-color } }
In Angular applications, DOM elements should not be obtained directly through native API or jQuery:
let element1 = document.getElementById("demop"); // jQuery获取: $('#demop')
Instead, you should get the DOM element through the method provided by Angular:
a728b34f8c39ac4b8264402fa7a79be6this is p!94b3e26ee717c64999d7867364b1b4a3 p的id：{{demop.id}} 56a354faacebef689e1d2dd71ed7d1a6
In the component template, we define the template of #demop on p variable, then demop is equal to the DOM object of p, so we can directly obtain the id of p throughdemop.id.
@ViewChild('demop') demop: ElementRef; // @ViewChild通过模板变量名获取 ngAfterViewInit() { console.log('p的id：' + this.demop.nativeElement.id); // p的id：demop }
In the component class, we obtain the ElementRef object that wraps the DOM object of p through @ViewChild. The ElementRef is defined as follows:
class ElementRef{ constructor(nativeElement: T) nativeElement: T }
So we can Get the DOM object of p through this.demop.nativeElement in ngAfterViewInit, and then get the id of the element.
has obtained the DOM object of p through several methods above, so how do we operate on it (setting styles, attributes, inserting sub-elements, etc.) ? Via raw API or jQuery is definitely not allowed.
In this way, we introduce the Angular abstract classRenderer2to set styles, attributes, insert sub-elements and other operations on elements.
Renderer2 is defined as follows:
class Renderer2 { get data: {...} destroyNode: ((node: any) => void) | null destroy(): void createElement(name: string, namespace?: string | null): any // 创建元素 createComment(value: string): any // 创建注释元素 createText(value: string): any // 创建文本元素 appendChild(parent: any, newChild: any): void // 添加子元素（在最后） insertBefore(parent: any, newChild: any, refChild: any): void // 添加子元素（在最前） removeChild(parent: any, oldChild: any): void // 移除子元素 selectRootElement(selectorOrNode: string | any): any // 获取根元素 parentNode(node: any): any // 获取父元素 nextSibling(node: any): any // 获取下一个兄弟元素 setAttribute(el: any, name: string, value: string, namespace?: string | null): void // 设置属性 removeAttribute(el: any, name: string, namespace?: string | null): void // 移除属性 addClass(el: any, name: string): void // 添加样式类 removeClass(el: any, name: string): void // 移除样式类 setStyle(el: any, style: string, value: any, flags?: RendererStyleFlags2): void // 设置样式 removeStyle(el: any, style: string, flags?: RendererStyleFlags2): void // 移除样式 setProperty(el: any, name: string, value: any): void // 设置DOM对象属性，不同于元素属性 setValue(node: any, value: string): void // 设置元素值 listen(target: 'window' | 'document' | 'body' | any, eventName: string, callback: (event: any) => boolean | void): () => void // 注册事件 }
Therefore, if we want to change the background color of p, we can do this:
ngAfterViewInit() { this.renderer.setStyle(this.demop.nativeElement, 'background-color', 'red'); // 通过Renderer2设置p的css样式background-color }
Related Recommended:
Angular Development Practice (5): In-depth Analysis of Change Monitoring
Angular Development Practice (6): Server-side Rendering
Angular Development Practice (1): Environment Preparation and Framework Construction
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