判断是不是允许输入特殊字符 _Web前端

判断是否允许输入特殊字符

<html>
<head>
<title>JS判断是否允许输入数字</title>
<script type="text/javascript">
function check(e){
??? var keynum
??? if(window.event){
? ??? keynum = e.keyCode;
? }
??? else if(e.which){
? ??? keynum = e.which;
? }
? if ((keynum>32&&keynum<48)||(keynum>57&&keynum<65)||(keynum>90&&keynum<97)||keynum==34||keynum==39||keynum==60||keynum==62){alert('请不要使用特殊字符');event.returnValue = false;}
}
</script>
</head>
<body>
<textarea rows=2 cols=20 name=comments
onKeypress="return check(event);"></textarea>
</body>
</html>