data.PHP
<?PHP header("Content-type: text/html; charset=utf-8"); $val = $_GET['q']; $regular = '/^[A-Z]/'; if (!preg_match($regular,$val)) { echo '用户名不合法'; } ?>
<html>
<head>
<script type="text/javascript">
function showHint(str)
{
var xmlhttp;
if (str.length==0)
{
document.getElementById("txtHint").innerHTML="";
return;
}
if (window.XMLHttpRequest)
{// code for IE7+,Firefox,Chrome,Opera,Safari
xmlhttp=new XMLHttpRequest();
}
else
{// code for IE6,IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function()
{
if (xmlhttp.readyState==4 && xmlhttp.status==200)
{
document.getElementById("txtHint").innerHTML=xmlhttp.responseText;
}
}
xmlhttp.open("GET","data.PHP?q="+str,true);
xmlhttp.send();
}
</script>
</head>
<body>
<h3>请在下面的输入框中键入字母（A - Z）：</h3>
<form action="">
<p>姓氏：<input type="text" id="txt1" onkeyup="showHint(this.value)" /><span id="txtHint"></span></p>
<input type="reset">
</form>
</body>
</html>
效果图:
原文链接：https://www.f2er.com/ajax/165171.html
