达到特定字符数后，如何防止输入到文本区域? [英] How to prevent input to a textarea after a certain character count is reached?

问题描述

使用以下代码，将删除超过指定最大值的所有输入.但这会产生一种效果，先键入一个字符，然后立即将其删除.我只想简单地阻止输入字符.

Using the below code, any input exceeding the specified maximum is removed. But this creates an effect where a character is typed and then immediately removed. I would prefer to simply prevent characters from being inputted.

<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>

推荐答案

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

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