ajax进度条

.graph { width: 400px; height: 25px; border: 1px solid #f8b3d0; }
.bar { background-color: #ffe7f4; display: block; float: left; height: 100%; text-align: center; }

<div class="fz">
    <div class="graph" id="graph">
        <em id="bar" class="bar"></em>
    </div>
    <input type="button" value="加载" id="btn">
    <em id="mes"></em>
</div>

$("#btn").bind("click", function () {
        startLoading();
    })
    var xmlHttp;
    var percent;
    function createXMLHttpRequest() {
        if (window.ActiveXObject) {
            xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
        }
        else if (window.XMLHttpRequest) {
            xmlHttp = new XMLHttpRequest();
        }
    }
    function startLoading() {
        createXMLHttpRequest();
        var url = "data.txt";
        xmlHttp.open("GET", url, true);
        xmlHttp.onreadystatechange = function () {
            if (xmlHttp.readyState == 4) {
                if (xmlHttp.status == 200) {
                    setTimeout("sendData()", 2000);
                }
            }
        };
        xmlHttp.send(null);
    }
    function sendData() {
        createXMLHttpRequest();
        var url = "data.txt";
        xmlHttp.open("GET", url, true);
        xmlHttp.onreadystatechange = function () {
            if (xmlHttp.readyState == 4) {
                if (xmlHttp.status == 200) {
                    percent = parseInt(xmlHttp.responseText);
                    refreshBar(percent);
                    if (percent < 100) {
                        setTimeout("sendData()", 2000);
                    }
                    else {
                        $("#mes").html("加载完毕");
                        //隐藏操作
                    }
                }
            }
        }
        xmlHttp.send(null);
    }
    //更新进度条
    function refreshBar(per) {
        $("#bar").width(per + "%");
    }

根目录下新建data.txt 。内容输入20

每2分钟请求一次data.txt。当data.txt的内容变为100时