原生Ajax

    <script type="text/javascript">
        //1 创建xhr对象
        var xhr = createXHR();
        function createXHR() {
            var request;
            if (typeof (XMLHttpRequest) == "undefined") {
                //ie老版本中创建的方式
                request = new ActiveXObject("Microsoft.XMLHTTP");
            } else {
                //支持标准的浏览器创建的方式
                request = new XMLHttpRequest();
            }
            return request;
        }

        window.onload = function () {
            document.getElementById("txt").onkeyup = function () {
                var txt = this;
                //判断是否有mydiv
                var mydiv = document.getElementById("mydiv");
                if (mydiv) {
                    document.getElementById("container").removeChild(mydiv);
                }

                if (this.value.length <= 0) {
                    return;
                }

                //2
                xhr.open("get", "defalut.ashx?wd=" + this.value, true);
                //3
                xhr.onreadystatechange = function () {
                    if (xhr.readyState == 4)
                    {
                        if (xhr.status == 200) {
                            var r = xhr.responseText;
                            //把字符串转换成数组对象
                            var array = eval(r);
                            //动态生成div
                            var div = document.createElement("div");
                            div.id = "mydiv";
                            document.getElementById("container").appendChild(div);

                            //
                            var ul = document.createElement("ul");
                            div.appendChild(ul);

                            for (var i = 0; i < array.length; i++) {
                                var li = document.createElement("li");
                                li.innerHTML = array[i];
                                ul.appendChild(li);

                                li.onmouseover = function () {
                                    this.style.backgroundColor = "red";

                                   txt.value =  this.innerHTML;
                                }

                                li.onmouseout = function () {
                                    this.style.backgroundColor = "";
                                }
                            }
                        }
                    }
                }
                //4
                xhr.send();
            }
        }
    </script>