自定义select，根据某项条件禁止选择，形成事件联动的解决

需要注意点有

text

1> 事件的产生的先后顺序
2> 事件内容状态的暂存

代码如下

<!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>Document</title>
</head>
<style>
    body,
    p,
    ul,
    li {
        padding: 0;
        margin: 0;
    }

    li {
        list-style: none;
    }

    .list {
        margin: 50px;
    }

    .content {
        position: relative;
        width: 150px;
        height: 25px;
        border: 1px solid gray;
    }

    .content:after {
        content: '';
        position: absolute;
        right: 0;
        top: 0;
        height: 25px;
        width: 25px;
        background: gray;
    }

    .select-ul {
        display: none;
        width: 150px;
    }

    .select-ul li {
        width: 150px;
        border: 1px solid red;
    }

    .caret {
        position: absolute;
        top: 0;
        right: 0;
        width: 25px;
        height: 25px;
    }

    .caret:after {
        content: '';
        position: absolute;
        border-width: 5px;
        border-style: solid;
        left: 10px;
        top: 8px;
        z-index: 15;
        border-color: transparent transparent transparent red;
        transition: all 0.1s linear;
        transform: rotate(0deg);
    }

    .caret_after:after {
        border-width: 5px;
        border-style: solid;
        border-color: transparent transparent transparent red;
        transform: rotate(90deg);
    }
    .para{
        text-align:center;
        height:100%;
    }

    .restrict{
        background:black;
        display: inline-block;
        color:white;
        padding:5px;
        border:3px;
        cursor: pointer;
        margin-right:10px;
    }
    .active{
        background:lawngreen;

    }
</style>

<body>
    <div class="list">
        <span class="active restrict">5</span>
        <span class="restrict">10</span>
        <span class="restrict">15</span>
        <span class="restrict">20</span>
        <div class="content">
            <p class="para">0</p>
            <span class="caret"></span>
        </div>
        <ul class="select-ul">
            <li>1</li>
            <li>2</li>
            <li>3</li>
            <li>4</li>
            <li>5</li>
            <li>6</li>
            <li>7</li>
            <li>8</li>
            <li>9</li>
            <li>10</li>
            <li>11</li>
            <li>12</li>
            <li>13</li>
            <li>14</li>
            <li>15</li>
            <li>16</li>
            <li>17</li>
            <li>18</li>
            <li>19</li>
        </ul>
    </div>
</body>
<script>
    var oUl = document.getElementsByClassName("select-ul")[0];
    var oContent = document.getElementsByClassName("content")[0];
    var oCaret = document.getElementsByClassName("caret")[0];
    var oPara = document.getElementsByClassName("para")[0];
    var oParaText = '';
    // 获得默认状态值
    oPara.onclick = function(){
        oParaText = this.textContent
    }
    // 判断是否展示自定义下拉框
    oContent.onclick = function () {
        if (oUl.style.display == "block") {
            oUl.style.display = "none";
            oCaret.classList.remove('caret_after');
            return;
        }
        oCaret.classList.add('caret_after');
        oUl.style.display = "block";
    }

    // 点击每个列表中的元素，并且赋值在选项框
    var oLi = document.getElementsByTagName("li");
    for (var i = 0; i < oLi.length; i++) {
        oLi[i].onclick = function () {
            if(Number(restrictSpanText) >= Number(this.textContent)){
                oPara.textContent = this.textContent;
            }
            else{
                oPara.textContent = oParaText;
                alert('所选数字大于限制数字,请重选');
            }
            oContent.click();
        }
    }
    // 捕获限制元素
    var oRestrict = document.getElementsByClassName("restrict");
    // 限制文本,默认设置个值
    var restrictSpanText = oRestrict[0].textContent;
    // 添加日期限制事件
    for(var i = 0; i< oRestrict.length;i++){
        oRestrict[i].onclick = function(){
            for(var j = 0 ; j < oRestrict.length;j++){
                if(Number(oPara.textContent)  > this.textContent){
                     alert("所选限制数字与文本框数字相矛盾，请重新选择");
                     return;
                }
                if(this!=oRestrict[j]){
                    oRestrict[j].classList.remove("active");
                }
                this.classList.add("active");
                restrictSpanText = this.textContent;
            }
        }
    }
</script>

</html>

补充2018-07-05 自定义下拉列表，并实现多选

代码如下，原理同上，注意的是字符间的空格

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>Document</title>
  </head>
  <style>
    body,
    p,
    ul,
    li {
      padding: 0;
      margin: 0;
    }

    li {
      list-style: none;
    }

    .list {
      margin: 50px;
    }

    .content {
      position: relative;
      width: 150px;
      height: 25px;
      border: 1px solid gray;
    }

    .content:after {
      content: "";
      position: absolute;
      right: 0;
      top: 0;
      height: 25px;
      width: 25px;
      background: gray;
    }

    .select-ul {
      display: none;
      width: 150px;
    }

    .select-ul li {
      width: 150px;
      border: 1px solid red;
    }

    .caret {
      position: absolute;
      top: 0;
      right: 0;
      width: 25px;
      height: 25px;
    }

    .caret:after {
      content: "";
      position: absolute;
      border-width: 5px;
      border-style: solid;
      left: 10px;
      top: 8px;
      z-index: 15;
      border-color: transparent transparent transparent red;
      transition: all 0.1s linear;
      transform: rotate(0deg);
    }

    .caret_after:after {
      border-width: 5px;
      border-style: solid;
      border-color: transparent transparent transparent red;
      transform: rotate(90deg);
    }

    .para {
      text-align: center;
      height: 100%;
    }
  </style>

  <body>
    <div class="list">
      <div class="content">
        <p class="para"></p>
        <span class="caret"></span>
      </div>
      <ul class="select-ul">
        <li><input type="checkbox" />1</li>
        <li><input type="checkbox" />2</li>
        <li><input type="checkbox" />3</li>
        <li><input type="checkbox" />4</li>
        <li><input type="checkbox" />5</li>
        <li><input type="checkbox" />6</li>
        <li><input type="checkbox" />7</li>
        <li><input type="checkbox" />8</li>
        <li><input type="checkbox" />9</li>
        <li><input type="checkbox" />10</li>
        <li><input type="checkbox" />11</li>
        <li><input type="checkbox" />12</li>
        <li><input type="checkbox" />13</li>
        <li><input type="checkbox" />14</li>
        <li><input type="checkbox" />15</li>
        <li><input type="checkbox" />16</li>
        <li><input type="checkbox" />17</li>
        <li><input type="checkbox" />18</li>
        <li><input type="checkbox" />19</li>
      </ul>
    </div>
  </body>
  <script>
    var oUl = document.getElementsByClassName("select-ul")[0];
    var oContent = document.getElementsByClassName("content")[0];
    var oCaret = document.getElementsByClassName("caret")[0];
    var oPara = document.getElementsByClassName("para")[0];
    // 判断是否展示自定义下拉框
    oContent.onclick = function () {
      if (oUl.style.display == "block") {
        oUl.style.display = "none";
        oCaret.classList.remove("caret_after");
        return;
      }
      oCaret.classList.add("caret_after");
      oUl.style.display = "block";
    };

    // 点击每个列表中的元素，并且赋值在选项框
    var oLi = document.getElementsByTagName("li");
    for (var i = 0; i < oLi.length; i++) {
      oLi[i].onclick = function (ev) {
        if (ev.target.nodeName.toLowerCase() == "input") {
          var existIndex = 0;
          if (this.getElementsByTagName("input")[0].checked) {
            if (!oPara.textContent.replace(/\s| /g, "")) {
              //因为本身html格式的原因【即换行的问题，所以即使数字去掉了，但会有换行和空格字符串，所以得把这两个给替换掉】，
              oPara.textContent = this.textContent;
            } else {
              oPara.textContent = oPara.textContent + "," + this.textContent;
            }
          } else {
            existIndex = oPara.textContent.indexOf(this.textContent);
            if (existIndex == oPara.textContent.length) {
              // 当字母为最后一个的时候
              oPara.textContent =
                oPara.textContent.slice(0, existIndex - 1) +
                oPara.textContent.slice(
                  existIndex + this.textContent.length,
                  oPara.textContent.length,
                );
            } else if (existIndex == 0) {
              // 当字母为第一个的时候
              oPara.textContent = oPara.textContent.slice(
                existIndex + this.textContent.length + 1,
                oPara.textContent.length,
              );
            } else {
              // 当字母为中间的时候
              oPara.textContent =
                oPara.textContent.slice(0, existIndex - 1) +
                oPara.textContent.slice(
                  existIndex + this.textContent.length,
                  oPara.textContent.length,
                );
            }
          }
        }
      };
    }
  </script>
</html>

自定义select，根据某项条件禁止选择，形成事件联动的解决 ​

补充2018-07-05 自定义下拉列表，并实现多选 ​

自定义select，根据某项条件禁止选择，形成事件联动的解决

补充2018-07-05 自定义下拉列表，并实现多选