js实现
<!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=gb2312" />
<title>无标题文档</title>
<script language="javascript">
function checkLength(which) {
var maxchar=100;
var oTextCount = document.getElementById("char");
iCount = which.value.replace(/[^\u0000-\u00ff]/g,"aa").length;
if(iCount<=maxchar)
{
oTextCount.innerHTML = "<font color=#FF0000>"+ iCount+"</font>";
which.style.border = '1px dotted #FF0000';
which.size=iCount+2;
}
else alert("请不要超过"+maxchar);
}
</script>
</head>
<body>
<input name="words" size="2" maxlength="100" onkeyup="checkLength(this)"/>
<span >0</span>个字符
</body>
</html>
jquery实现
<!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=gb2312" />
<title>无标题文档</title>
<script src="jquery-1.7.2.min.js"></script>
<script language="javascript">
function checkLength(which) {
iCount = which.value.replace(/[^\u0000-\u00ff]/g,"aa").length;
which.style.border = '1px dotted #FF0000';
which.size=iCount+2;
}
$(function() {
$("input").keyup(function(){checkLength(this);});
})
</script>
</head>
<body>
<input name="words" size="2" maxlength="100" class="add_page_input" />
</body>
</html>