有個需求是：輸入框有文字的時候就顯示清除按鈕，沒有文字則隱藏清除按鈕，點選清除按鈕不能影響鍵盤彈出的狀態。

網上有css實現自動顯示和隱藏清除按鈕的方案，但是考慮到相容性，我們還是使用js來實現。

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;
     };