可以，只需使用javascript获取文件，确保将文件作为数据URL读取。解析出base64之前的内容，以实际获得base64编码的数据，然后如果您使用php或任何后端语言，您可以解码base64数据并保存到如下所示的文件中

Javascript:
var reader = new FileReader();
reader.onloadend = function ()
{
  dataToBeSent = reader.result.split("base64,")[1];
  $.post(url, {data:dataToBeSent});
}
reader.readAsDataURL(this.files[0]);


PHP:
    file_put_contents('my.pdf', base64_decode($_POST["data"]));

当然，你可能会想做一些验证，比如检查你正在处理的文件类型之类的事情，但这是一个想法。

如许多答案所示，使用FormData是一种方法。这里有一些代码非常适合这个目的。我也同意嵌套ajax块以完成复杂环境的意见。通过包括e.PreventDefault（）；根据我的经验，使代码更易于跨浏览器兼容。

    $('#UploadB1').click(function(e){        
    e.preventDefault();

    if (!fileupload.valid()) {
        return false;            
    }

    var myformData = new FormData();        
    myformData.append('file', $('#uploadFile')[0].files[0]);

    $("#UpdateMessage5").html("Uploading file ....");
    $("#UpdateMessage5").css("background","url(../include/images/loaderIcon.gif) no-repeat right");

    myformData.append('mode', 'fileUpload');
    myformData.append('myid', $('#myid').val());
    myformData.append('type', $('#fileType').val());
    //formData.append('myfile', file, file.name); 

    $.ajax({
        url: 'include/fetch.php',
        method: 'post',
        processData: false,
        contentType: false,
        cache: false,
        data: myformData,
        enctype: 'multipart/form-data',
        success: function(response){
            $("#UpdateMessage5").html(response); //.delay(2000).hide(1); 
            $("#UpdateMessage5").css("background","");

            console.log("file successfully submitted");
        },error: function(){
            console.log("not okay");
        }
    });
});

可以，只需使用javascript获取文件，确保将文件作为数据URL读取。解析出base64之前的内容，以实际获得base64编码的数据，然后如果您使用php或任何后端语言，您可以解码base64数据并保存到如下所示的文件中

Javascript:
var reader = new FileReader();
reader.onloadend = function ()
{
  dataToBeSent = reader.result.split("base64,")[1];
  $.post(url, {data:dataToBeSent});
}
reader.readAsDataURL(this.files[0]);


PHP:
    file_put_contents('my.pdf', base64_decode($_POST["data"]));

当然，你可能会想做一些验证，比如检查你正在处理的文件类型之类的事情，但这是一个想法。

无法通过AJAX上载文件。您可以上传文件，而无需使用IFrame刷新页面。您可以在此处查看更多详细信息。

更新

XHR2支持通过AJAX上传文件。例如，通过FormData对象，但遗憾的是，它不受所有/旧浏览器的支持。

FormData支持从以下桌面浏览器版本开始。

即10+Firefox 4.0+铬7+Safari 5+歌剧12+

有关详细信息，请参阅MDN链接。

这是我的代码

var formData = new FormData();
var files = $('input[type=file]');
for (var i = 0; i < files.length; i++) {
if (files[i].value == "" || files[i].value == null) {
 return false;
}
else {
 formData.append(files[i].name, files[i].files[0]);
}
}
var formSerializeArray = $("#Form").serializeArray();
for (var i = 0; i < formSerializeArray.length; i++) {
  formData.append(formSerializeArray[i].name, formSerializeArray[i].value)
}
$.ajax({
 type: 'POST',
 data: formData,
 contentType: false,
 processData: false,
 cache: false,
 url: '/Controller/Action',
 success: function (response) {
 if (response.Success == true) {
    return true;
 }
 else {
    return false;
 }
 },
 error: function () {
   return false;
 },
 failure: function () {
   return false;
 }
 });

在通过ajax从预览中删除不需要的文件后，我实现了一个即时预览和上传的多文件选择。

详细文档可在以下位置找到：http://anasthecoder.blogspot.ae/2014/12/multi-file-select-preview-without.html

演示：http://jsfiddle.net/anas/6v8Kz/7/embedded/result/

jsFiddle：http://jsfiddle.net/anas/6v8Kz/7/

Java脚本：

    $(document).ready(function(){
    $('form').submit(function(ev){
        $('.overlay').show();
        $(window).scrollTop(0);
        return upload_images_selected(ev, ev.target);
    })
})
function add_new_file_uploader(addBtn) {
    var currentRow = $(addBtn).parent().parent();
    var newRow = $(currentRow).clone();
    $(newRow).find('.previewImage, .imagePreviewTable').hide();
    $(newRow).find('.removeButton').show();
    $(newRow).find('table.imagePreviewTable').find('tr').remove();
    $(newRow).find('input.multipleImageFileInput').val('');
    $(addBtn).parent().parent().parent().append(newRow);
}

function remove_file_uploader(removeBtn) {
    $(removeBtn).parent().parent().remove();
}

function show_image_preview(file_selector) {
    //files selected using current file selector
    var files = file_selector.files;
    //Container of image previews
    var imageContainer = $(file_selector).next('table.imagePreviewTable');
    //Number of images selected
    var number_of_images = files.length;
    //Build image preview row
    var imagePreviewRow = $('<tr class="imagePreviewRow_0"><td valign=top style="width: 510px;"></td>' +
        '<td valign=top><input type="button" value="X" title="Remove Image" class="removeImageButton" imageIndex="0" onclick="remove_selected_image(this)" /></td>' +
        '</tr> ');
    //Add image preview row
    $(imageContainer).html(imagePreviewRow);
    if (number_of_images > 1) {
        for (var i =1; i<number_of_images; i++) {
            /**
             *Generate class name of the respective image container appending index of selected images, 
             *sothat we can match images selected and the one which is previewed
             */
            var newImagePreviewRow = $(imagePreviewRow).clone().removeClass('imagePreviewRow_0').addClass('imagePreviewRow_'+i);
            $(newImagePreviewRow).find('input[type="button"]').attr('imageIndex', i);
            $(imageContainer).append(newImagePreviewRow);
        }
    }
    for (var i = 0; i < files.length; i++) {
        var file = files[i];
        /**
         * Allow only images
         */
        var imageType = /image.*/;
        if (!file.type.match(imageType)) {
          continue;
        }

        /**
         * Create an image dom object dynamically
         */
        var img = document.createElement("img");

        /**
         * Get preview area of the image
         */
        var preview = $(imageContainer).find('tr.imagePreviewRow_'+i).find('td:first');

        /**
         * Append preview of selected image to the corresponding container
         */
        preview.append(img); 

        /**
         * Set style of appended preview(Can be done via css also)
         */
        preview.find('img').addClass('previewImage').css({'max-width': '500px', 'max-height': '500px'});

        /**
         * Initialize file reader
         */
        var reader = new FileReader();
        /**
         * Onload event of file reader assign target image to the preview
         */
        reader.onload = (function(aImg) { return function(e) { aImg.src = e.target.result; }; })(img);
        /**
         * Initiate read
         */
        reader.readAsDataURL(file);
    }
    /**
     * Show preview
     */
    $(imageContainer).show();
}

function remove_selected_image(close_button)
{
    /**
     * Remove this image from preview
     */
    var imageIndex = $(close_button).attr('imageindex');
    $(close_button).parents('.imagePreviewRow_' + imageIndex).remove();
}

function upload_images_selected(event, formObj)
{
    event.preventDefault();
    //Get number of images
    var imageCount = $('.previewImage').length;
    //Get all multi select inputs
    var fileInputs = document.querySelectorAll('.multipleImageFileInput');
    //Url where the image is to be uploaded
    var url= "/upload-directory/";
    //Get number of inputs
    var number_of_inputs = $(fileInputs).length; 
    var inputCount = 0;

    //Iterate through each file selector input
    $(fileInputs).each(function(index, input){

        fileList = input.files;
        // Create a new FormData object.
        var formData = new FormData();
        //Extra parameters can be added to the form data object
        formData.append('bulk_upload', '1');
        formData.append('username', $('input[name="username"]').val());
        //Iterate throug each images selected by each file selector and find if the image is present in the preview
        for (var i = 0; i < fileList.length; i++) {
            if ($(input).next('.imagePreviewTable').find('.imagePreviewRow_'+i).length != 0) {
                var file = fileList[i];
                // Check the file type.
                if (!file.type.match('image.*')) {
                    continue;
                }
                // Add the file to the request.
                formData.append('image_uploader_multiple[' +(inputCount++)+ ']', file, file.name);
            }
        }
        // Set up the request.
        var xhr = new XMLHttpRequest();
        xhr.open('POST', url, true);
        xhr.onload = function () {
            if (xhr.status === 200) {
                var jsonResponse = JSON.parse(xhr.responseText);
                if (jsonResponse.status == 1) {
                    $(jsonResponse.file_info).each(function(){
                        //Iterate through response and find data corresponding to each file uploaded
                        var uploaded_file_name = this.original;
                        var saved_file_name = this.target;
                        var file_name_input = '<input type="hidden" class="image_name" name="image_names[]" value="' +saved_file_name+ '" />';
                        file_info_container.append(file_name_input);

                        imageCount--;
                    })
                    //Decrement count of inputs to find all images selected by all multi select are uploaded
                    number_of_inputs--;
                    if(number_of_inputs == 0) {
                        //All images selected by each file selector is uploaded
                        //Do necessary acteion post upload
                        $('.overlay').hide();
                    }
                } else {
                    if (typeof jsonResponse.error_field_name != 'undefined') {
                        //Do appropriate error action
                    } else {
                        alert(jsonResponse.message);
                    }
                    $('.overlay').hide();
                    event.preventDefault();
                    return false;
                }
            } else {
                /*alert('Something went wrong!');*/
                $('.overlay').hide();
                event.preventDefault();
            }
        };
        xhr.send(formData);
    })

    return false;
}