一款輪播插件的誕生

時間 2019-11-05

標籤一款插件誕生简体版

原文原文鏈接

1. 前言

早在幾個月前，就想本身動手寫個輪播圖組件，所以也看了許多文章，斷斷續續過了幾個月，今天終於有時間騰出手來給此插件作個總結，所以有了這篇文章。話很少說，先上 Demo, 效果以下：javascript

2. HTML and CSS

本文不討論html,css的實現方式，直接貼上代碼css

<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <title>Suporka Vue App</title>
  </head>
  <body>
    <div id="carousal">
      <!--左箭頭-->
      <button
        type="button"
        class="suporka-carousel__arrow suporka-carousel__arrow--left"
        style=""
        id="suporka-prev-btn"
      >
        &lt;
      </button>
      <div id="wrapper">
        <div class="box">
          <img
            src="https://zxpsuper.github.io/Demo/carousal/banner1.jpg"
            alt=""
          />
        </div>
        <div class="box">
          <img
            src="https://zxpsuper.github.io/Demo/carousal/banner2.jpg"
            alt=""
          />
        </div>
        <div class="box">
          <img
            src="https://zxpsuper.github.io/Demo/carousal/banner3.jpg"
            alt=""
          />
        </div>
        <div class="box">
          <img
            src="https://zxpsuper.github.io/Demo/carousal/banner4.jpg"
            alt=""
          />
        </div>
      </div>
      <!--右箭頭-->
      <button
        type="button"
        class="suporka-carousel__arrow suporka-carousel__arrow--right"
        style=""
        id="suporka-next-btn"
      >
        &gt;
      </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>

/*樣式代碼*/
* {
  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 實現輪播圖功能

本插件是用 es6 寫的，固然考慮兼容性，你能夠選擇 babel 進行編譯，本文不作闡述。html

1. 首先，建立一個 carousal 類

它有一些默認參數，如time（圖片輪播間隔），transition (轉場動畫時間)，autoScroll（是否自動輪播）,showDot（是否顯示底部小圓點）。而後將頁面的一些元素掛載在類的屬性上。java

class Carousal {
    constructor(userOption) {
    this.option = {
      time: 4000,
      transition: 0.8,
      autoScroll: true,
      showDot: false
    };
    // 當前索引
    this.number = 1;
    // 定時器
    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

固然，默認參數是能夠修改的，因此類傳入了一個 userOption 對象, 在構造函數中將用戶設置的參數覆蓋默認參數，在this.init(userOption) 方法中執行覆蓋。node

輪播圖輪播的原理是：在輪播圖組首位添加一個末位圖片的副本，同時也在輪播圖末位添加一個首位圖片的副本，大概就是 5 1 2 3 4 5 1 , 此時共有7張圖片，當向右輪播至第七張圖片‘1’ 時, 取消transition後輪播圖定位至第二張圖片 ‘1’, 此時再度開啓transition 。同理，向左輪播至第一張圖片「5」時，也會取消transition後輪播圖定位至第六張圖片 ‘5’, 然後再度開啓 transition。git

所以，咱們須要手動在dom結構中插入這兩個首尾圖片。pushItem() 方法正是爲此而生。es6

class Carousal {
    //...
  init(userOption) {
    // 合併用戶配置
    if (Object.assign) {
      Object.assign(this.option, userOption);
    } else {
      // 不支持 Object.assign 就調用 extend 方法
      this.extend(this.option, userOption, true);
    }
    // 設置動畫 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();
  }
  // 合併屬性方法
  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; // 獲取輪播圖寬度
    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";
  }
}

插入輪播圖片以後，判斷是否須要插入底部小圓點。requestAnimFrame()用於實現持續的動畫效果。github

class Carousal {
    init() {
        //...續 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');
        }
        // 判斷是否開啓自動輪播，如是則自動輪播
        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. 加入事件監聽

監聽鼠標移入事件，當鼠標移入的時候，中止自動滾動。web

監聽左右按鈕的點擊，執行上一張，下一張圖的輪播效果。npm

class Carousal {
    init() {
        //...續 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;
        }
    }
    // 事件監聽
    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. 自動輪播

定時動畫，而且若是存在底部小圓點，修改其類名，達到與輪播圖同步的效果。

// 自動輪播
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);
    }
    // 開始移動
    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);
    }
    // 設置小圓點樣式
    setDotClass(parent, index, cls) {
        // 沒有小圓點就返回
        if (!this.dot) return false;
        for (let i = 0; i < parent.length; i++) {
            removeClass(parent[i], cls);
        }
        addClass(parent[index], cls);
    }
}

// 三個類名操做方法
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. 實現上一張，下一張輪播功能

class Carousal {
    //...
    // prev上一張
    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'
            );
    }
    // 下一張
    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'
            );
    }
    // 去到最後一張
    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.優化及其餘

最後，代碼需通過babel轉譯，而且以 umd 的形式支持瀏覽器直接引入，requirejs 及 commonjs 導入，詳細作法能夠參考我以前的一篇文章《ES6 手寫一個「辨色」小遊戲》。也能夠參考我在 github 上的代碼, 歡迎 fork and star .

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