一款轮播组件的诞生

一时失言乱红尘 2022-04-10 06:19 235阅读 0赞

## 1. 前言 ##

早在几个月前，就想自己动手写个轮播图组件，因此也看了许多文章，断断续续过了几个月，今天终于有时间腾出手来给此插件做个总结，因此有了这篇文章。话不多说，先上 [Demo][], 效果如下：

![20181228102121813][]

## 2. HTML and CSS ##

本文不讨论html,css的实现方式，直接贴上代码

\`\`\` <!DOCTYPE html> <html> <head> <meta charset="UTF-8" /> <title>Suporka Vue App</title> </head> <body> <div id="carousal">  <button type="button" class="suporka-carousel\_\_arrow suporka-carousel\_\_arrow--left" style="" id="suporka-prev-btn" > < </button> <div id="wrapper"> <div class="box"> <img src="http://h5.sztoda.cn/static/img/loveLetter/teacher/teacher1.jpg" alt="" /> </div> <div class="box"> <img src="http://h5.sztoda.cn/static/img/loveLetter/teacher/teacher2.jpg" alt="" /> </div> <div class="box"> <img src="http://h5.sztoda.cn/static/img/loveLetter/teacher/teacher3.jpg" alt="" /> </div> <div class="box"> <img src="http://h5.sztoda.cn/static/img/loveLetter/teacher/teacher4.jpg" alt="" /> </div> </div>  <button type="button" class="suporka-carousel\_\_arrow suporka-carousel\_\_arrow--right" style="" id="suporka-next-btn" > > </button> </div> <script src="https://cdn.jsdelivr.net/npm/suporka-carousal@1.0.3/carousal.js"></script> <script> new Carousal(\{ autoScroll: true, showDot: true \}); </script> </body> </html> \`\`\`

/*样式代码*/
    * {
      margin: 0;
      padding: 0;
    }
    div {
      margin: 0;
      border: 0;
      padding: 0;
    }
    #carousal {
      width: 557px;
      overflow: hidden;
      position: relative;
    }
    #wrapper {
      display: box; /* OLD - Android 4.4- */
      display: -webkit-box; /* OLD - iOS 6-, Safari 3.1-6 */
      display: -moz-box; /* OLD - Firefox 19- (buggy but mostly works) */
      display: -ms-flexbox; /* TWEENER - IE 10 */
      display: -webkit-flex; /* NEW - Chrome */
      display: flex;
      -webkit-flex-wrap: nowrap;
      -moz-flex-wrap: nowrap;
      -ms-flex-wrap: nowrap;
      -o-flex-wrap: nowrap;
      flex-wrap: nowrap;
      white-space: nowrap;
      position: relative;
      left: 0;
    }
    .suporka-carousel__arrow {
      /* display: none; */
      border: none;
      outline: none;
      padding: 0;
      margin: 0;
      height: 36px;
      width: 36px;
      cursor: pointer;
      transition: 0.3s;
      border-radius: 50%;
      background-color: rgba(31, 45, 61, 0.5);
      color: #fff;
      position: absolute;
      top: 50%;
      z-index: 10;
      transform: translateY(-50%);
      text-align: center;
      font-size: 12px;
      font-weight: 600;
    }
    .suporka-carousel__arrow--right {
      right: -38px;
    }
    .suporka-carousel__arrow--left {
      left: -38px;
    }
    #carousal:hover > .suporkal-carousel__arrow {
      display: block;
    }
    #carousal:hover .suporka-carousel__arrow--right {
      right: 16px;
    }
    #carousal:hover .suporka-carousel__arrow--left {
      left: 16px;
    }
    #suporka-dot {
      position: absolute;
      bottom: 20px;
      left: 50%;
      transform: translate(-50%, 0);
    }
    #suporka-dot span {
      width: 10px;
      height: 10px;
      border-radius: 50%;
      margin: 0 10px;
      display: inline-block;
      background: #999;
    }
    #suporka-dot .suporka-dot--acitve {
      background: #fff;
    }

## 3. javascript 实现轮播图功能 ##

本插件是用 es6 写的，当然考虑兼容性，你可以选择 babel 进行编译，本文不做阐述。

### 1. 首先，创建一个 carousal 类 ###

它有一些默认参数，如time（图片轮播间隔），transition (转场动画时间)，autoScroll（是否自动轮播）,showDot（是否显示底部小圆点）。然后将页面的一些元素挂载在类的属性上。

class Carousal {
        constructor(userOption) {
        this.option = {
          time: 4000,
          transition: 0.8,
          autoScroll: true,
          showDot: false
        };
        // 当前索引
        this.number = 1;
        // 定时器
        this.timer = null;
        this.interval = null;
        this.carousal = document.getElementById("carousal");
        this.wrapper = document.querySelector("#wrapper");
        this.childrenLength: document.getElementById("wrapper").children.length;
        this.init(userOption);
      }
    }

### 2. 初始化dom ###

当然，默认参数是可以修改的，所以类传入了一个 userOption 对象, 在构造函数中将用户设置的参数覆盖默认参数，在this.init(userOption) 方法中执行覆盖。

轮播图轮播的原理是：在轮播图组首位添加一个末位图片的副本，同时也在轮播图末位添加一个首位图片的副本，大概就是 `5 1 2 3 4 5 1`, 此时共有7张图片，当向右轮播至第七张图片‘1’ 时, 取消transition后轮播图定位至第二张图片 ‘1’, 此时再度开启transition 。同理，向左轮播至第一张图片“5”时，也会取消transition后轮播图定位至第六张图片 ‘5’, 而后再度开启 transition。

因此，我们需要手动在dom结构中插入这两个首尾图片。pushItem() 方法正是为此而生。

class Carousal {
        //...
      init(userOption) {
        // 合并用户配置
        if (Object.assign) {
          Object.assign(this.option, userOption);
        } else {
          // 不支持 Object.assign 就调用 extend 方法
          this.extend(this.option, userOption, true);
        }
        // 设置动画 transition
        this.wrapper.style.transition = `all ${this.option.transition}s`;
        this.wrapper.style["-moz-transition"] = `all ${this.option.transition}s`;
        this.wrapper.style["-webkit-transition"] = `all ${this.option.transition}s`;
        this.wrapper.style["-o-transition"] = `all ${this.option.transition}s`;
        // 首尾添加元素
        this.pushItem();
      }
      // 合并属性方法
      extend(o, n, override) {
        for (var p in n) {
          if (n.hasOwnProperty(p) && (!o.hasOwnProperty(p) || override))
            o[p] = n[p];
        }
      }
      // 初始化添加首尾子元素
      pushItem() {
        let movePx = this.carousal.offsetWidth; // 获取轮播图宽度
        let first = this.wrapper.children[0].cloneNode(true);
        let last = this.wrapper.children[this.childrenLength - 1].cloneNode(true);
        let parent = this.wrapper;
        parent.appendChild(first);
        parent.insertBefore(last, parent.children[0]);
        this.wrapper.style.left =
          this.wrapper.offsetLeft - movePx + "px";
      }
    }

插入轮播图片之后，判断是否需要插入底部小圆点。requestAnimFrame()用于实现持续的动画效果。

class Carousal {
        init() {
            //...续 this.pushItem();
            if (this.option.showDot) {
                let node = document.createElement('div');
                node.setAttribute('id', 'suporka-dot');
                node.innerHTML = `${'<span></span>'.repeat(this.childrenLength)}`;
                this.carousal.appendChild(node);
                this.dot = document.getElementById('suporka-dot');
                this.dot.firstChild.setAttribute('class', 'suporka-dot--acitve');
            }
            // 判断是否开启自动轮播，如是则自动轮播
            if (this.option.autoScroll) this.requestAnimFrame(this.autoMove());
        }
        requestAnimFrame() {
            return (
                window.requestAnimationFrame ||
                window.webkitRequestAnimationFrame ||
                window.mozRequestAnimationFrame ||
                window.oRequestAnimationFrame ||
                window.msRequestAnimationFrame ||
                function(callback) {
                    window.setTimeout(callback, 1000 / 60);
                }
            );
        }
    }

### 3. 加入事件监听 ###

监听鼠标移入事件，当鼠标移入的时候，停止自动滚动。

监听左右按钮的点击，执行上一张，下一张图的轮播效果。

class Carousal {
        init() {
            //...续 if (this.option.autoScroll) this.requestAnimFrame(this.autoMove());
            this.addEventListener();
        }
        // 添加事件
        addEvent(element, type, handler) {
            if (element.addEventListener) {
                element.addEventListener(type, handler, false);
            } else if (element.attachEvent) {
                element.attachEvent('on' + type, handler);
            } else {
                element['on' + type] = handler;
            }
        }
        // 事件监听
        addEventListener() {
            if (this.option.autoScroll) {
                this.addEvent(this.carousal, 'mouseover', event => {
                    clearInterval(this.interval);
                });
                this.addEvent(this.carousal, 'mouseout', event => {
                    this.autoMove();
                });
            }
            let prev = document.getElementById('suporka-prev-btn');
            let next = document.getElementById('suporka-next-btn');
            if (prev && next) {
                this.addEvent(prev, 'click', event => {
                    this.prev();
                });
                this.addEvent(next, 'click', event => {
                    this.next();
                });
            }
        }
    }

### 4. 自动轮播 ###

定时动画，并且如果存在底部小圆点，修改其类名，达到与轮播图同步的效果。

// 自动轮播
    class Carousal {
        // ...
        autoMove() {
            let movePx = this.carousal.offsetWidth;
            this.interval = setInterval(() => {
                this.number += 1;
                this.wrapper.style.left = 0 - movePx * this.number + 'px';
                if (this.number === this.childrenLength + 1) this.startMove();
                if (this.dot)
                    this.setDotClass(
                        this.dot.children,
                        this.number - 1,
                        'suporka-dot--acitve'
                    );
            }, this.option.time);
        }
        // 开始移动
        startMove() {
            this.number = 1;
            this.timer = setTimeout(() => {
                this.wrapper.style.transition = `none`;
                this.wrapper.style.left = -this.carousal.offsetWidth + 'px';
                setTimeout(() => {
                    this.wrapper.style.transition = `all ${
                        this.option.transition
                    }s`;
                }, 100);
            }, this.option.transition * 1000);
        }
        // 设置小圆点样式
        setDotClass(parent, index, cls) {
            // 没有小圆点就返回
            if (!this.dot) return false;
            for (let i = 0; i < parent.length; i++) {
                removeClass(parent[i], cls);
            }
            addClass(parent[index], cls);
        }
    }
    
    // 三个类名操作方法
    function hasClass(ele, cls) {
        if (ele.className)
            return ele.className.match(new RegExp('(\\s|^)' + cls + '(\\s|$)'));
        else return false;
    }
    function addClass(ele, cls) {
        if (!hasClass(ele, cls)) ele.className += ' ' + cls;
    }
    function removeClass(ele, cls) {
        if (hasClass(ele, cls)) {
            let reg = new RegExp('(\\s|^)' + cls + '(\\s|$)');
            ele.className = ele.className.replace(reg, ' ');
        }
    }

### 5. 实现上一张，下一张轮播功能 ###

class Carousal {
        //...
        // prev上一张
        prev() {
            let movePx = this.carousal.offsetWidth;
            this.number -= 1;
    
            this.wrapper.style.left = 0 - movePx * this.number + 'px';
            if (this.number === 0) this.goLastOne();
            if (this.dot)
                this.setDotClass(
                    this.dot.children,
                    this.number - 1,
                    'suporka-dot--acitve'
                );
        }
        // 下一张
        next() {
            let movePx = this.carousal.offsetWidth;
            this.number += 1;
            this.wrapper.style.left = 0 - movePx * this.number + 'px';
            if (this.number === this.childrenLength + 1) this.startMove();
            if (this.dot)
                this.setDotClass(
                    this.dot.children,
                    this.number - 1,
                    'suporka-dot--acitve'
                );
        }
        // 去到最后一张
        goLastOne() {
            this.number = this.childrenLength;
            this.timer = setTimeout(() => {
                this.wrapper.style.transition = `none`;
                this.wrapper.style.left =
                    -this.carousal.offsetWidth * this.childrenLength + 'px';
                setTimeout(() => {
                    this.wrapper.style.transition = `all ${
                        this.option.transition
                    }s`;
                }, 100);
            }, this.option.transition * 1000);
        }
    }

## 4.优化及其他 ##

最后，代码需经过babel转译，并且以 umd 的形式支持浏览器直接引入，requirejs 及 commonjs 导入，详细做法可以参考我之前的一篇文章[《ES6 手写一个“辨色”小游戏》][ES6]。也可以参考我在 [github][] 上的代码, 欢迎 fork and star .

来源：[https://segmentfault.com/a/1190000017541904][https_segmentfault.com_a_1190000017541904]

[Demo]: https://zxpsuper.github.io/Demo/carousal/index.html
[20181228102121813]: /images/20220402/0acb1507b6d5456498c6100daee74516.png
[ES6]: https://juejin.im/user/5af17df4518825672a02e1f5/posts
[github]: https://github.com/zxpsuper/Demo
[https_segmentfault.com_a_1190000017541904]: https://segmentfault.com/a/1190000017541904