用AJAX从PHP 文件返回数据 - 自学教程(runoops.com)

<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <title>用AJAX从PHP 文件返回数据 - 自学教程(runoops.com)</title>
    <script>
        function showHint(str) {
            var xmlhttp;
            if (str.length == 0) {
                document.getElementById("txtHint").innerHTML = "";
                return;
            }
            if (window.XMLHttpRequest) {
                // IE7+, Firefox, Chrome, Opera, Safari 浏览器执行代码
                xmlhttp = new XMLHttpRequest();
            }
            else {
                // IE6, IE5 浏览器执行代码
                xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
            }
            xmlhttp.onreadystatechange = function () {
                if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
                    document.getElementById("txtHint").innerHTML = xmlhttp.responseText;
                }
            }
            xmlhttp.open("GET", "//demo.runoops.com/ajax/gethint.php?q=" + str, true);
            xmlhttp.send();
        }
    </script>
</head>

<body>

<h3>在输入框中尝试输入字母 a:</h3>
    <form action="">
        输入姓名: <input type="text" id="txt1" onkeyup="showHint(this.value)" />
    </form>
    <p>提示信息: <span id="txtHint"></span></p>

</body>

</html>