JavaScript实现实时字数统计：onKeyup事件应用与优化

HTML与JavaScript实现代码

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>测试文件</title>
<script>
function cal_words(){
  var length = document.getElementById("test").value.length;
  document.getElementById("num").innerHTML = length;
}
</script>
</head>

<body>
<div class="reply">
 <textarea id="test" onKeyUp="cal_words()"></textarea>
 <div>字数：<span id="num">0</span></div>
</div>
</body>
</html>