前端analysis | 3w & 1h

《angular8》- 你需要了解的Render2

2020-06-09

Render2

介绍

Render2 是angular中用于操作dom的，Angular做了封装，屏蔽底层差异，通用性更强。不仅仅可以用于浏览器端，还可以用于Server Side rendering, Web-Worker, mobile apps, and desktop apps等。

Render2之指令用法

  • setStyle、removeStyle

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    # 定义指令
     import { Directive, ElementRef, OnInit, Renderer2, HostListener } from '@angular/core';
     @Directive({ 
         selector: '[animate]' 
     })
     export class Animate  {
     constructor(private renderer: Renderer2, private el: ElementRef) {}
         
     @HostListener('click') 
     performTask() {
         let randomColor = "#"+((1<<24)*Math.random()|0).toString(16);
         this.renderer.setStyle(this.el.nativeElement, 'color', randomColor);
         this.renderer.setStyle(this.el.nativeElement, 'background-color', 'black');   
         this.renderer.removeStyle(this.el.nativeElement, 'color','red');   
     }

     }
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    # html
    <h2  animate>Click here to give me a random color</h2>

  • setAttribute、removeAttribute

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     @Directive({ 
         selector: '[defaultValue]' 
    })
    export class DefaultInputValueDirective {
       constructor(private elRef: ElementRef, private renderer: Renderer2) {
       }
       @HostListener('mouseover') 
       onMouseOver() {
           this.renderer.setAttribute(this.elRef.nativeElement, 'value', 'Enter a Value');
       }
       @HostListener('mouseleave') 
       onMouseLeave() {
           this.renderer.removeAttribute(this.elRef.nativeElement, 'value');
       }   
    }

  • addClass、removeClass

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     @Directive({ 
         selector: '[hlOnMouseOver]' 
    })
    export class HlOnMouseOverDirective {
       constructor(private elRef: ElementRef, private renderer: Renderer2) {
       }
       @HostListener('mouseover') 
       onMouseOver() {
           this.renderer.addClass(this.elRef.nativeElement, 'hl-text');
       }
       @HostListener('mouseleave') 
       onMouseLeave() {
           this.renderer.removeClass(this.elRef.nativeElement, 'hl-text');
       }   
    }

  • removeChild、appendChild

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     @Directive({ 
         selector: '[removeChild]' 
    })
    export class RemoveChildDirective {
       constructor(private elRef: ElementRef, private renderer: Renderer2) {
       }
       p = this.renderer.createElement('p');
       text = this.renderer.createText('Hello World !');
       
       @HostListener('mouseover') 
       onMouseOver() {
           this.renderer.appendChild(this.p, this.text);  
           this.renderer.appendChild(this.elRef.nativeElement, this.p);
       }
       @HostListener('mouseleave') 
       onMouseLeave() {
           this.renderer.removeChild(this.elRef.nativeElement, this.p);
       }   
    }

  • setProperty

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     @Directive({ 
         selector: '[imgAlt]' 
    })
    export class ImageAltdDirective {
       constructor(private renderer: Renderer2, private elRef: ElementRef) {}

       ngOnInit() {
         this.renderer.setProperty(this.elRef.nativeElement, 'alt', 'image description');
       }

    }

Render2之组件用法 - 大部分构造方法只有Renderer2

  • viewChild操作dom appendChild

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    import { Component, ElementRef, Renderer2, ViewChild } from '@angular/core';

    @Component({
       selector: 'app-component',
       template: `<ul class="col-md-2">
                    <li (click)="addBtn()" #addButton>Click here to add new button</li>
                  </ul> 
                  `
    })

    export class AppComponent { 
       @ViewChild('addButton') 
       private animateThis: ElementRef;	
       constructor(private renderer: Renderer2) {}
       
       addBtn() {
         const button = this.renderer.createElement('button'); 
         const buttonText = this.renderer.createText('This is a button');
         this.renderer.appendChild(button, buttonText);
         this.renderer.appendChild(this.animateThis.nativeElement, button);
       }
    } 
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    # html
    <ul class="col-md-2">
      <li (click)="addBtn()" #addButton>Click here to add new button</li>
    </ul>

  • insertBefore 、createComment

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    import { Component, ElementRef, Renderer2, ViewChild } from '@angular/core';

    @Component({
       selector: 'app-component',
       template: `<ul class="col-md-2">
                    <li (click)="addBtn()" #addButton>Click here to add new button</li>
                  </ul> 
                  `
    })

    export class AppComponent { 
       @ViewChild('addButton') 
       private animateThis: ElementRef;	
       constructor(private elRef: ElementRef, private renderer: Renderer2) {}
       
       addBtn() {
         const button = this.renderer.createElement('button'); 
         const buttonText = this.renderer.createText('This is a button');
         const comment = this.renderer.createComment('createComment? Comment Created!');
         const parent = this.elRef.nativeElement.parentNode;
         const reference = this.elRef.nativeElement;
         this.renderer.appendChild(button, buttonText);
         this.renderer.insertBefore(parent, comment, reference )
         this.renderer.appendChild(this.animateThis.nativeElement, button);
       }
    }

  • setStyle

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    import { Component, ViewChild, ElementRef, Renderer2  } from '@angular/core';

    @Component({
      selector: 'my-app',
      template: `
        Username: 
        <input type="text" placeholder="type your name..."  #changeStyle>
      `,
    })
    export class AppComponent  {
       @ViewChild('changeStyle') 
       private elRef: ElementRef;	
       constructor(private renderer: Renderer2) {}
       
       ngOnInit() {
         this.renderer.setStyle(this.elRef.nativeElement, 'border', '1px solid red');
       }
    }

  • addClass

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    import { Component, ViewChild, ElementRef, Renderer2  } from '@angular/core';

    @Component({
      selector: 'my-app',
      template: `
        Username: 
        <input type="text" placeholder="type your name..."  #changeStyle>
      `,
    })
    export class AppComponent  {
       @ViewChild('changeStyle') 
       private elRef: ElementRef;	
       constructor(private renderer: Renderer2) {}
       
       ngOnInit() {
         this.renderer.addClass(this.elRef.nativeElement, 'someClass');
       }
      
      //HTML output
      //<input placeholder="type your name..." type="text" class="someClass">
    }

  • setAttribute

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    import { Component, ViewChild, ElementRef, Renderer2  } from '@angular/core';

    @Component({
      selector: 'my-app',
      template: `
        Username: 
        <input type="text" placeholder="type your name..."  #changeStyle>
      `,
    })
    export class AppComponent  {
       @ViewChild('changeStyle') 
       private elRef: ElementRef;	
       constructor(private renderer: Renderer2) {}
       
       ngOnInit() {
         this.renderer.setAttribute(this.elRef.nativeElement, 'value', 'Gokhan');
       }
    }

  • setProperty

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    import { Component, ViewChild, ElementRef, Renderer2  } from '@angular/core';

    @Component({
      selector: 'my-app',
      template: `
        Username: 
        <input type="text" placeholder="type your name..."  #changeStyle>
      `,
    })
    export class AppComponent  {
       @ViewChild('changeStyle') 
       private elRef: ElementRef;	
       constructor(private renderer: Renderer2) {}
       
       ngOnInit() {
          this.renderer.setProperty(this.elRef.nativeElement, 'disabled', 'disabled');
          this.renderer.setProperty(this.elRef.nativeElement, 'innerHTML', change the inner html');
       }
    }

  • nextSibling

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    import { Component, Renderer2, ElementRef, ViewChild, OnInit } from '@angular/core';

    @Component({
      selector: 'my-app',
      template: `
        <p #next>First</p>
        <p>Second</p>
        <p>Third</p>
      `,
      styleUrls: [ './app.component.css' ]
    })
    export class AppComponent implements OnInit {
      @ViewChild('next') 
      private elRef: ElementRef;	
      constructor(private renderer: Renderer2) {}

      ngOnInit(){
        const currentElement = this.elRef.nativeElement;
        const nextEl = this.renderer.nextSibling(currentElement);
        this.renderer.addClass(nextEl, 'red');
      }

    }

  • parentNode

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    import { Component, Renderer2, ElementRef, ViewChild, OnInit } from '@angular/core';

    @Component({
      selector: 'my-app',
      template: `
        <div>
          <p #parent>First</p>
          <p>Second</p>
          <p>Third</p>
        </div>
          `,
      styleUrls: [ './app.component.css' ]
    })
    export class AppComponent implements OnInit {
      @ViewChild('parent') 
      private elRef: ElementRef;	
      constructor(private renderer: Renderer2) {}

      ngOnInit(){
        const currentElement = this.elRef.nativeElement;
        const parent = this.renderer.parentNode(currentElement);
        this.renderer.addClass(parent, 'red');
      }

    }

  • selectRootElement

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    # selectRootElement(selectorOrNode: any, preserveContent?: boolean) - 是否保留子内容

    import { Component, Renderer2, ElementRef, ViewChild, OnInit } from '@angular/core';

    @Component({
      selector: 'my-app',
      template: `
            <div #root>
            X or Y?
            </div> 
            <button (click)="changeIt()">Click</button>
          `,
      styleUrls: [ './app.component.css' ]
    })
    export class AppComponent {
      switchText: boolean = false;
      @ViewChild('root') 
      private elRef: ElementRef;	
      constructor(private renderer: Renderer2) {}
      changeIt(){
        this.switchText = !this.switchText;
        const rootEl = this.elRef.nativeElement;
        const text = this.switchText ? 
          this.renderer.createText('Hey X!') :
          this.renderer.createText('Hey Y!');
        this.renderer.selectRootElement(rootEl); 
        this.renderer.appendChild(rootEl, text)
      }

    }
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    # 源码
    selectRootElement(selector: string): Element {
        var el = DOM.querySelector(this._rootRenderer.document, selector);
        if (isBlank(el)) {
          throw new BaseException(`The selector "${selector}" did not match any elements`);
        }
        DOM.clearNodes(el);
        return el;
     }

  • listen

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    import { Component, ViewChild, ElementRef, Renderer2 } from '@angular/core';

    @Component({
      selector: 'my-app',
      template: `
        <p #listen>
          Hover to see some magic!
        </p>
        {{count}}
      `,
    })
    export class AppComponent  {
      @ViewChild('listen') 
        private elRef: ElementRef;	
        constructor(private renderer: Renderer2) {
        }
        toggle = false; 
        count = 0;  
        ngAfterViewInit() {
        this.renderer.listen(this.elRef.nativeElement, 'mouseover', () => {
          this.toggle = !this.toggle;
          this.count++;
          const currentElement = this.elRef.nativeElement;
          const firstText = this.renderer.createText('Hover to see new text! (Hover me)');
          const secondText = this.renderer.createText('Text changed! (Hover me)');
          const thirdText = this.renderer.createText('Reached maximum count!');

          this.renderer.selectRootElement(currentElement);
          if(this.count < 10){
              this.toggle ? this.renderer.appendChild(currentElement, secondText) : 
              this.renderer.appendChild(currentElement, firstText);
          } else {
              this.renderer.appendChild(currentElement, thirdText);
              this.count = 10;
          }

        });
      }
    }

参考

Angular Render2

本文作者：前端analysis
联系邮箱：cheonghu@126.com
版权声明： 本文章除特别声明外，均采用 CC BY-NC-SA 4.0 许可协议。转载请注明出处！
Tags: angular render2
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