相关疑难解决方法(0)

我试图发送一些表单而不重新加载页面,我试图理解引擎盖下的细节,因此不使用任何JavaScript库:

var http = createRequestObject();
function createRequestObject() {
    var objAjax;
    if (window.XMLHttpRequest)
    {// code for IE7+, Firefox, Chrome, Opera, Safari
        objAjax=new XMLHttpRequest();
    }
    else
    {// code for IE6, IE5
        objAjax=new ActiveXObject("Microsoft.XMLHTTP");
    }
    return objAjax;
}

function display_progress() { ... }    

function upload_file() {
    var request = 'UploaderServlet';
    http.open('post', request);
    http.onreadystatechange = display_progress;
    http.send(null); // HERE PROBABLY THE DATA SHOULD BE SENT
}

<form enctype="multipart/form-data" id="upload_form" name="upload_form" method="POST" action="UploaderServlet" onsubmit="upload_file(); return false;" target="upload_target">
Choose a file <br />  
<input name="file" size="27" …

这是我的javascript

function ajax_post(){
            // Create our XMLHttpRequest object
            var hr = new XMLHttpRequest();
            // Create some variables we need to send to our PHP file
            var url = "LiveUpdate.php";
            var sb = document.getElementById("LiveUpdate").value;
            var FirstName = document.getElementById("FirstName").value;
            var images = document.getElementById("images").value;

            var vars = "update="+sb+"&FirstName="+FirstName+"&images="+images;
            hr.open("POST", url, true);
            // Set content type header information for sending url encoded variables in the request
            hr.setRequestHeader("Content-type", "multipart/form-data");
            // Access the onreadystatechange event for the XMLHttpRequest object
            hr.onreadystatechange = function() {
                if(hr.readyState == 4 …