js代码小记（判断textbox的长度，并且固定最多收入字符）_javascript教程教程_H5之家

<!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>Untitled Document</title>
<SCRIPT language=javascript1.3><!--
var testleng=300;//允许多少字符串填入

function GC_UpdateCharCount() {
var desc_el = document.getElementById('desc');
var remainingchars_el = document.getElementById('remainingchars');

var num_remaining = testleng - desc_el.value.length;

if (num_remaining >= 0) {
remainingchars_el.innerHTML = num_remaining;
} else {
remainingchars_el.innerHTML = "<font color=red>" +
(-num_remaining + '') + " characters over</font>";
}
}
function isOver(sText)
            {
                var intlen=sText.value.length;
                if (intlen>testleng)
                {
                    alert("描述特征的内容的字数必修小于或者等于 "+testleng);
                    sText.focus();
                    sText.select();
                }
            }

//--></SCRIPT>
</head>

<body>
<<B>Group description</B><BR><TEXTAREA id=desc onkeydown=GC_UpdateCharCount() onkeyup=GC_UpdateCharCount() onblur="isOver(this);"style="WIDTH: 99%" name=desc rows=4 cols=50></TEXTAREA>
            <BR>Letters remaining: <SPAN id=remainingchars>
            <SCRIPT language=javascript1.2></SCRIPT></SPAN><NOSCRIPT>300 characters allowed </NOSCRIPT>
</body>
</html>