js

 document.getElementById('ll').onclick = function () {     var input = document.getElementById("kw"); 
            var value = input.value; 
            var newValue = value.replace(/[0-9]/g,''); 
            input.value = newValue;
         };

html

<textarea   placeholder="内容框"  id="kw"></textarea>
  
  
  
<a id="ll">清除数字</a>