js：输入字数限制

Demo
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>字数限制</title>
</head>
<body>
<textarea id="b" rows="4" cols="20" ></textarea>
<div><span id="a">已输入字符: </span><input type="button" value="OK" onclick="cha()"></div>
<script language="javascript">
var maxl=3//总长
document.onkeydown=function(){
   var s=document.getElementById("b").value.length +1;
   if(s>maxl)document.getElementById("b").value=document.getElementById("b").value.substr(0,maxl-1)
   else document.getElementById("a").innerHTML="已输入："+s+"/"+maxl+" 字符"
}
</script>
</body>
</html>

 

posted @ 2013-10-24 11:07  tinyphp  Views(311)  Comments(0)    收藏  举报