html移动应用 input 标签 清除按钮功能如何实现（不触发键盘）

有个需求是：输入框有文本的时候就显示清除按钮，没有文本则隐藏清除按钮，点击清除按钮不能影响键盘弹出的状态。

网上有css实现自动显示和隐藏清除按钮的方案，但是考虑到兼容性，我们还是使用js来实现。

css

---

body{
             background: #eee;
         }
         form{
             margin: 30px 0;
             position: relative;
         }
         #keyword{
             height: 90px;
             font-size: 60px;
             line-height: 90px;
             width: 300px;
         }
         #clear{
             color: red;
             width: 90px;
             height: 90px;
             line-height: 90px;
             text-align: center;
             position: absolute;
             top: 0;
             left: 210px;
             visibility:hidden;
         }

---

html

---

<form onsubmit="return false;" >
     <input type="button" id="clear" value="clear">
     <input type="search" id="keyword">
</form>

---

js

---

var keyword = document.getElementById('keyword'),
         clear=document.getElementById('clear'),
         autoShow=function () {
         clear.style.display=keyword.value.length>0?'block':'none';
         clear.style.visibility=keyword.value.length>0?'visible':'hidden';
     };

keyword.oninput=autoShow;

clear.onmousedown=function (e) {
         keyword.value = '';
         autoShow();
         keyword.focus();
         e.preventDefault();
         e.stopPropagation();
         return false;
     };

---