老师，麻烦看下这个问题

base.js
import {ELEMENT_NODE_TYPE} from './constants';

import DEFAULTS from './default';



class BaseSlider {
    constructor(el) {
        if (el.nodeType !== ELEMENT_NODE_TYPE) {
          throw new Error('实例化的时候，请传入 DOM 元素！');
        }
  
      实际参数
      this.options = {
        ...DEFAULTS,
        ...options
      };

        const sliderEL = el;

        const sliderContentEl = sliderEL.querySelector(".slider-content");
        const sliderItemEls = sliderContentEl.querySelectorAll(".slider-item");

        //添加到this上，为了在方法使用
        this.sliderEL = sliderEL;
        this.sliderContentEl = sliderContentEl;
        this.sliderItemEls = sliderItemEls;
        
        this.minIndex = 0;
        this.maxIndex = sliderItemEls.length - 1;
        
        this.currIndex = this.getCorrectedIndex(this.options.initiallindex,
            );

        //每个slider-item 的宽度（每次移动的距离）
        this.itemWidth = sliderItemEls[0].offsetWidth;

        this.init();

       }
       //初始化
       init(){
        //    为每个slider-item设置宽度
        this.setItemsWidth();

        // 为slider-content设置宽度
        this.setContentWidth();
       }

        // 为每个slider-item设置宽度
        setItemsWidth(){
            for(const item of this.sliderItemEls){
                item.style.width = `${this.itemWidth}px`;
            }
        }

        // 为slider-content设置宽度
        setContentWidth(){
            this.sliderContentEl.style.width = `${this.itemWidth * this.sliderItemEls.length}px`;
       }

        //获取修正后的索引值
        getCorrectedIndeex(index){
            if(index<this.minIndex) return this.maxIndex;
            if(index>this.minIndex) return this.minIndex;
            return index;
        }


}



export default BaseSlider;

constants.js
//keyboard
export const LEDT_KEYCODE = 37;
export const RIGHT_KEYCODE = 39;

 //base
 export const ELEMENT_NODE_TYPE = 1;
 
 default.js
 //默认参数
const DEFAULTS = {
    //初始索引
    initiallindex:0,
    //切换时是否有动画
    Animation:true,
    //切换速度，单位ms
    speed:300,
    //自动切换，单位ms
    autoplay:0
};

export default DEFAULTS;

index.js
import BaseSlider from './base.js';
import keyboard from './keyboard.js';

// 继承基类
class Slider extends BaseSlider {
  constructor(el) {
    super(el);

    this.bindEvent();
  }

  bindEvent() {
    keyboard.bindEvent(this);
  }
}

export default Slider;

keyboard.js
// 添加键盘控制
import { LEFT_KEYCODE, RIGHT_KEYCODE } from './constants.js';

const keyboard = {
  bindEvent(slider) {
    document.addEventListener(
      'keyup',
      ev => {
        if (ev.keyCode === LEFT_KEYCODE) {
          slider.prev();
        } else if (ev.keyCode === RIGHT_KEYCODE) {
          slider.next();
        }
      },
      false
    );
  }
};

export default keyboard;

slider/index.js
import './slider.css'

import Slider from './module';

new Slider(document.querySelector('slider'));

slider.art
<div class="slider">
    <ul class="slider-content">
        <li class="slider-item">
            <a href="#">
                <img src="images/banner1.jpg" alt="" class="slider-img">
            </a>
        </li>
        <li class="slider-item">
            <a href="#">
                <img src="images/banner2.jpg" alt="" class="slider-img">
            </a>
        </li>
        <li class="slider-item">
            <a href="#">
                <img src="images/banner3.jpg" alt="" class="slider-img">
            </a>
        </li>
        <li class="slider-item">
            <a href="#">
                <img src="images/banner4.jpg" alt="" class="slider-img">
            </a>
        </li>
        <li class="slider-item">
            <a href="#">
                <img src="images/banner5.jpg" alt="" class="slider-img">
            </a>
        </li>
    </ul>
</div>

​slider.css
​.slider,
.slider-content,
.slider-item,
.slider-img {
  width: 100%;
  height: 100%;
}
.slider {
  overflow: hidden;
}
.slider-item {
  float: left;
}
.slider-img {
  /* display: block; */
  vertical-align: top;
}
.slider-animation {
  transition-property: transform;
  transition-duration: 0ms;
}

el. nodetype 获取不到

base.js
​import {ELEMENT_NODE_TYPE} from './constants';

import DEFAULTS from './default';



class BaseSlider {
    constructor(el,options) {
    console.log(el);
        if (el.nodeType !== ELEMENT_NODE_TYPE) {
          throw new Error('实例化的时候，请传入 DOM 元素！');
        }

      实际参数
      this.options = {
        ...DEFAULTS,
        ...options
      };

        const sliderEL = el;

        const sliderContentEl = sliderEL.querySelector(".slider-content");
        const sliderItemEls = sliderContentEl.querySelectorAll(".slider-item");

        //添加到this上，为了在方法使用
        this.sliderEL = sliderEL;
        this.sliderContentEl = sliderContentEl;
        this.sliderItemEls = sliderItemEls;

        this.minIndex = 0;
        this.maxIndex = sliderItemEls.length - 1;

        this.currIndex = this.getCorrectedIndex(this.options.initiallindex,
            );

        //每个slider-item 的宽度（每次移动的距离）
        this.itemWidth = sliderItemEls[0].offsetWidth;

        this.init();

       }
       //初始化
       init(){
        //    为每个slider-item设置宽度
        this.setItemsWidth();

        // 为slider-content设置宽度
        this.setContentWidth();
       }

        // 为每个slider-item设置宽度
        setItemsWidth(){
            for(const item of this.sliderItemEls){
                item.style.width = `${this.itemWidth}px`;
            }
        }

        // 为slider-content设置宽度
        setContentWidth(){
            this.sliderContentEl.style.width = `${this.itemWidth * this.sliderItemEls.length}px`;
       }

        //获取修正后的索引值
        getCorrectedIndeex(index){
            if(index<this.minIndex) return this.maxIndex;
            if(index>this.minIndex) return this.minIndex;
            return index;
        }


}



export default BaseSlider;

index.js
import BaseSlider from './base.js';
import keyboard from './keyboard.js';

// 继承基类
class Slider extends BaseSlider {
  constructor(el,options) {
    super(el,options);

    this.bindEvent();
  }

  bindEvent() {
    keyboard.bindEvent(this);
  }
}

export default Slider;

base.js和index.js用下面这个 ，

老师 我已经测试好了。一个很简单的小错误，自己没细心处理好 谢谢了