<head>
<meta http-equiv="x-ua-compatible" content="IE=EmulateIE7" />
<title></title>
<!-- http://www.cnblogs.com/babycool -->
<script src="../js/jquery-1.7.2.min.js" type="text/javascript"></script>
<script type="text/javascript">
$(function () {
$("#xxxxxx").keyup(function () {
//如果输入非数字，则替换为‘‘，如果输入数字，则在每4位之后添加一个空格分隔
this.value = this.value.replace(/[^\d]/g, ‘‘).replace(/(\d{4})(?=\d)/g, "$1 ");
})
});
</script>
</head>
<body>
限制只能输入19个字符
<input id="xxxxxx" type="text" name="name" value="" maxlength="19" />
<br />
<br />
输入非数字替换为‘‘
<input type="text" name="name" value="" onkeyup="value=value.replace(/[^\d]/g,‘‘)" />
<br />
<br />
</body>
原文：http://www.cnblogs.com/shy1766IT/p/5184886.html