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删除使用bind添加的事件侦听器(此)

removeeventlistener custom-element addeventlistener ecmascript-6 javascript

connexo · 技术社区 · 6 年前

去除单击我绑定到的侦听器 window constructor 在下面我需要它来听 窗口

class MyEl extends HTMLButtonElement {
  constructor() {
    super();
    this.clickCount = 0;
    window.addEventListener('click', this.clickHandler.bind(this));
  }
  
  clickHandler(e) {
    if (e.target === this) {
      this.textContent = `clicked ${++this.clickCount} times`;
      window.removeEventListener('click', this.clickHandler);
    }
  }
  
  disconnectedCallback() {
      window.removeEventListener('click', this.clickHandler);
  }
}

customElements.define('my-el', MyEl, { extends: 'button' });

<button is="my-el" type="button">Click me</button>

2 回复 | 直到 6 年前

CertainPerformance 6 年前

您当前的实现不可能做到这一点,因为 .bind removeEventListener 如果传递的函数相同,则删除侦听器( === addEventListener (就像 .includes .has 适用于(套):

const fn = () => 'foo';
console.log(fn.bind(window) === fn.bind(window));

作为一种解决方法,您可以将绑定函数分配给实例的属性:

class MyEl extends HTMLButtonElement {
  constructor() {
    super();
    this.clickCount = 0;
    this.boundListener = this.clickHandler.bind(this);
    window.addEventListener('click', this.boundListener);
  }
  
  clickHandler(e) {
    this.textContent = `clicked ${++this.clickCount} times`;
    window.removeEventListener('click', this.boundListener);
  }
}

customElements.define('my-el', MyEl, { extends: 'button' });

<button is="my-el" type="button">Click me</button>

kockburn 6 年前

class MyEl extends HTMLButtonElement {
  constructor() {
    super();
    this.clickCount = 0;
    this.wrapper = e => this.clickHandler.apply(this, e);
    window.addEventListener('click', this.wrapper);
  }
  
  clickHandler(e) {
    this.textContent = `clicked ${++this.clickCount} times`;
    
    window.removeEventListener('click', this.wrapper);
  }
}

customElements.define('my-el', MyEl, { extends: 'button' });

<button is="my-el" type="button">Click me</button>

Danny '365CSI' Engelman 4 年前

另一个 模式是保持你的听众 在…内 构造器。

要删除事件侦听器(无论采用何种模式),可以添加“删除” 功能创建事件侦听器的那一刻。

从那以后功能在 listen name 和 func 激动

伪代码:

  listen(name , func){
    window.addEventListener(name, func);
    return () => window.removeEventListener( name , func );
  }

  let remove = listen( 'click' , () => alert('BOO!') );

  //cleanup:
  remove();

运行代码段

不断涌现的事件&阴影区

为了节省一个小时,一旦你做更多的活动。。。

请注意,网络组件(即CustomElements 具有 shadowDOM)需要使用 composed:true 向上的 越过它的阴影边界

    new CustomEvent("check", {
      bubbles: true,
      //cancelable: false,
      composed: true       // required to break out of shadowDOM
    });

删除添加的事件侦听器

注意:此示例不在Safari上运行,因为Apple拒绝实现扩展元素: extends HTMLButtonElement

class MyEl extends HTMLButtonElement {
  constructor() {
    let ME = super();// super() retuns this scope; ME makes code easier to read
    let count = 0;// you do not have to stick everything on the Element
    ME.mute = ME.listen('click' , event => {
      //this function is in constructor scope, so has access to ALL its contents
      if(event.target === ME) //because ALL click events will fire!
        ME.textContent = `clicked ${ME.id} ${++count} times`;
      //if you only want to allow N clicks per button you call ME.mute() here
    });
  }

  listen(name , func){
    window.addEventListener( name , func );
    console.log('added' , name , this.id );
    return () => { // return a Function!
      console.log( 'removeEventListener' , name , 'from' , this.id);
      this.style.opacity=.5;
      window.removeEventListener( name , func );
    }
  }
  eol(){ // End of Life
    this.parentNode.removeChild(this);
  }
  disconnectedCallback() {
      console.log('disconnectedCallback');
      this.mute();
  }
}

customElements.define('my-el', MyEl, { extends: 'button' });

button{
  width:12em;
}

<button id="One" is="my-el" type="button">Click me</button>
<button onclick="One.mute()">Mute</button> 
<button onclick="One.eol()">Delete</button> 
<br>
<button id="Two" is="my-el" type="button">Click me too</button>
<button onclick="Two.disconnectedCallback()">Mute</button> 
<button onclick="Two.eol()">Delete</button>

笔记:

count this.count
onclick=Two.disconnectedCallback() 正如示例所示,该函数不会删除元素。

另见: https://pm.dartus.fr/blog/a-complete-guide-on-shadow-dom-and-event-propagation/