达到某个字符数后,如何防止输入textarea？

Question

使用以下代码,将删除超出指定最大值的任何输入.但这会产生一种效果,即键入一个字符然后立即删除.我宁愿简单地阻止输入字符.

<textarea  id="textarea" onKeyDown="limitText()" onKeyUp="limitText()">
</textarea> 
<span name="charcount_text" id="charcount_text"></span>

  <script type="text/javascript">
    function limitText() {
      var count = document.getElementById('textarea').value.length;
      var remaining = 4000 - count;
      if(remaining <= 0) {
        document.getElementById('charcount_text').innerHTML = '4000 character limit reached.' ;
        document.getElementById('textarea').value = document.getElementById('textarea').value.substring(0, 4000);
      } else if(remaining <= 50) {
        document.getElementById('charcount_text').innerHTML = '4000 character limit, ' + remaining  + ' remaining.';
      } else {
        document.getElementById('charcount_text').innerHTML = '';
      }
    }
  </script>

Answer 1

使用maxlength属性:

<textarea  id="textarea" maxlength="4000" onkeyup="limitText()"></textarea>

function limitText() {
  var ta= document.getElementById('textarea'),
      count= ta.value.length,
      ml= ta.maxLength,
      remaining= ml - count,
      cc= document.getElementById('charcount_text');

  if(remaining <= 0) {
    cc.innerHTML = ml+' character limit reached.' ;
  } else if(remaining <= 50) {
    cc.innerHTML = ml+' character limit, ' + remaining  + ' remaining.';
  } else {
    cc.innerHTML = '';
  }
}

小提琴