js选项卡切换实例

https://www.bilibili.com/video/av82185698?p=17，视频外加自己完善了点代码，加了点注释

tab.js

// var that;
//存在问题，选项卡长度做出了我的0-8字限制，但是不太地道
class Tab {
    
    
    constructor(id) {
    
    
        // that = this;//看es6.0 class比对，指向自己
        this.main = document.querySelector(id);
        this.add = this.main.querySelector('.tabadd');
        // li的父元素，CSS3选择器
        this.ul = this.main.querySelector('.fisrstnav ul:first-child');
        this.fsection = this.main.querySelector('.tabscon');// section 父元素
        this.init();
    }
    init() {
    
    
            this.updateNode();
            // init 初始化操作让相关的元素绑定事件
            this.add.onclick = this.addTab.bind(this.add, this);
            for (var i = 0; i < this.lis.length; i++) {
    
    
                this.lis[i].index = i;
                // this.lis[i].onclick = this.toggleTab;//不能加括号，不然直接调用了
                this.lis[i].onclick = this.toggleTab.bind(this.lis[i], this);
                this.remove[i].onclick = this.removeTab.bind(this.remove[i], this);
                this.spans[i].ondblclick = this.editTab;
                this.sections[i].ondblclick = this.editTab;
            }
        }
        // 因为动态添加元素 需要从新获取对应的元素个数
    updateNode() {
    
    
            this.lis = this.main.querySelectorAll('li');
            this.sections = this.main.querySelectorAll('section');
            this.remove = this.main.querySelectorAll('.icon-guanbi');
            this.spans = this.main.querySelectorAll('.fisrstnav li span:first-child');
        }
        // 1. 切换功能
    toggleTab(that) {
    
    
            // console.log(this.index);
            that.clearClass();//顺序，为什么用that，因为this指向下没有sections属性，谁onclick，this指向谁
            this.className = 'liactive';//this指向小li
            that.sections[this.index].className = 'conactive';
    }
    // 清除所有li 和section 的类
    clearClass() {
    
    
            for (var i = 0; i < this.lis.length; i++) {
    
    
                this.lis[i].className = '';
                this.sections[i].className = '';
            }
        }
        // 2. 添加功能
    addTab(that) {
    
    
            that.clearClass();//不然会有一堆li选中，以及一堆section框堆在下面
            // (1) 创建li元素和section元素
            if(that.lis.length + 1 <= 8){
    
    
                var li = '<li class="liactive"><span>新选项卡</span><span class="iconfont icon-guanbi"></span></li>';
                var section = '<section class="conactive">请在输入框输入文字</section>';
                // (2) 把这两个元素追加到对应的父元素里面
                that.ul.insertAdjacentHTML('beforeend', li);
                that.fsection.insertAdjacentHTML('beforeend', section);
                //以前的做法:动态创建元素createElement，但是元素里面内容较多，需要innerHTML赋值在appendChild追加到父元素里面.
                //现在高级做法:利用insertAdjacentHTML()可以直接把字符串格式元素添加到父元素中
                //beforebegin afterbegin beforeend afterend
                //appendChild不支持追加字符串的子元素, insertAdjacentHTML支持追加字符串的元素
                that.init();//先获取元素再重新获取各种事件，不然没有切换功能（init），没有清除class样式（updateNode）
            }else{
    
    
                var index = this.previousElementSibling.lastElementChild.index;
                // console.log(index);
                that.lis[index] && that.lis[index].click();
                alert("最多允许8个选项卡");
            }
        }
        // 3. 删除功能
    removeTab(that, e) {
    
    
            e.stopPropagation(); // 阻止冒泡 防止触发li 的切换点击事件
            var index = this.parentNode.index;
            console.log(index);
            // 根据索引号删除对应的li 和section   remove()方法可以直接删除指定的元素
            that.lis[index].remove();
            that.sections[index].remove();
            that.init();
            // 如果删除的不是选中状态的li，原来的选中状态li保持不变，有类就代表选中
            if (document.querySelector('.liactive')) return;
            // 当我们删除了选中状态的这个li 的时候, 让它的前一个li 处于选定状态
            index--;
            // 手动调用我们的点击事件  不需要鼠标触发，第一个条件是防止为选项卡为0情况下就是下标为-1
            that.lis[index] && that.lis[index].click();
        }
        // 4. 修改功能
    editTab() {
    
    
        var str = this.innerHTML;
        // 双击禁止选中文字，固定代码
        window.getSelection ? window.getSelection().removeAllRanges(): document.selection.empty();
        // 双击时生成文本框，失去焦点/按回车 则传值
        this.innerHTML = '<textarea wrap="virtual"></textarea>';//用input输入时是单行
        var textarea = this.children[0];
        textarea.value = str;
        textarea.select(); // 文本框里面的文字处于选定状态
        if(this.nodeName == 'SPAN'){
    
    //防止span和section都做出0-8限制
            // 当我们离开文本框就把文本框里面的值给span
            textarea.onblur = function() {
    
    
                if(this.value.length <= 8 && this.value.length > 0 ) {
    
    //其实光是限制长度不太地道
                    this.parentNode.innerHTML = this.value;
                }
                else if(this.value.length == 0){
    
    
                    this.parentNode.innerHTML = str;
                    alert("至少输入1个字");
                }
                else {
    
    
                    this.parentNode.innerHTML = str;
                    alert("最多允许8个字符");
                }
            };
        }
        else if(this.nodeName == 'SECTION'){
    
    
            textarea.onblur = function() {
    
    
                this.parentNode.innerHTML = this.value;
            }
        }
        // 按下回车也可以把文本框里面的值给span
        textarea.onkeyup = function(e) {
    
    
            if (e.keyCode === 13) {
    
    
                // 手动调用表单失去焦点事件  不需要鼠标离开操作
                this.blur();
            }
        }
    }
}
new Tab('#tab');

index.html

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>面向对象 Tab</title>
    <link rel="stylesheet" href="./styles/tab.css">
    <link rel="stylesheet" href="./styles/style.css">
</head>

<body>

    <main>
        <h4>
            Js 面向对象 动态添加标签页
        </h4>
        <div class="tabsbox" id="tab">
            <!-- tab 标签 -->
            <nav class="fisrstnav">
                <ul>
                    <li class="liactive"><span>选项卡1</span><span class="iconfont icon-guanbi"></span></li>
                    <li><span>选项卡2</span><span class="iconfont icon-guanbi"></span></li>
                    <li><span>选项卡3</span><span class="iconfont icon-guanbi"></span></li>
                </ul>
                <div class="tabadd">
                    <span>+</span>
                </div>
            </nav>

            <!-- tab 内容 -->
            <div class="tabscon">
<!--                <textarea class="conactive">请在输入框输入文字</textarea>-->
                <section class="conactive">请在输入框输入文字</section>
                <section>请在输入框输入文字</section>
                <section>请在输入框输入文字</section>
            </div>
        </div>
    </main>

    <script src="js/tab.js"></script>
</body>

</html>

style.css

@font-face {
    
    font-family: "iconfont";
  src: url('./iconfont/iconfont.eot?t=1553960438096'); /* IE9 */
  src: url('./iconfont/iconfont.eot?t=1553960438096#iefix') format('embedded-opentype'), /* IE6-IE8 */
  url('data:application/x-font-woff2;charset=utf-8;base64,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') format('woff2'),
  url('./iconfont/iconfont.woff?t=1553960438096') format('woff'),
  url('./iconfont/iconfont.ttf?t=1553960438096') format('truetype'), /* chrome, firefox, opera, Safari, Android, iOS 4.2+ */
  url('./iconfont/iconfont.svg?t=1553960438096#iconfont') format('svg'); /* iOS 4.1- */
}

.iconfont {
    
    
  font-family: "iconfont" !important;
  font-size: 16px;
  font-style: normal;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

.icon-guanbi:before {
    
    
  content: "\e676";
}

tab.css

* {
    
    
    margin: 0;
    padding: 0;
}

ul li {
    
    
    list-style: none;
}

main {
    
    
    width: 960px;
    height: 500px;
    border-radius: 10px;
    margin: 50px auto;
}

main h4 {
    
    
    height: 100px;
    line-height: 100px;
    text-align: center;
}

.tabsbox {
    
    
    width: 900px;
    margin: 0 auto;
    height: 400px;
    border: 1px solid lightsalmon;
    position: relative;
}

nav ul {
    
    
    overflow: hidden;
}

nav ul li {
    
    
    float: left;
    width: 100px;
    height: 50px;
    line-height: 50px;
    text-align: center;
    border-right: 1px solid #ccc;
    position: relative;
}

nav ul li.liactive {
    
    
    border-bottom: 2px solid #fff;
    z-index: 9;
}

#tab textarea {
    
    
    width: 80%;
    height: 60%;
}

nav ul li span:last-child {
    
    
    position: absolute;
    user-select: none;
    font-size: 12px;
    top: -18px;
    right: 0;
    display: inline-block;
    height: 20px;
}

.tabadd {
    
    
    position: absolute;
    /* width: 100px; */
    top: 0;
    right: 0;
}

.tabadd span {
    
    
    display: block;
    width: 20px;
    height: 20px;
    line-height: 20px;
    text-align: center;
    border: 1px solid #ccc;
    float: right;
    margin: 10px;
    user-select: none;
}

.tabscon {
    
    
    width: 100%;
    height: 300px;
    position: absolute;
    padding: 30px;
    top: 50px;
    left: 0px;
    box-sizing: border-box;
    border-top: 1px solid #ccc;
}

.tabscon section,
.tabscon section.conactive {
    
    
    display: none;
    width: 100%;
    height: 100%;
}

.tabscon section.conactive {
    
    
    display: block;
}

iconfont文件没法放