Question

假设我正在如片段代码中所示从中上传一个文件，然后再次从同一上传click控件中上传两个文件，在这种情况下，旧文件会从文件上传控件中松脱，而新上传的文件会悬停显示上传控制

复制步骤：

1）当我单击“选择附件”按钮选择一个文件时，视图如下图所示

2）现在，当我再次单击“选择附件”按钮选择两个图像时，旧图像/文件将被删除，新文件将被显示。请在下面的屏幕截图中查看

3）单击删除后，旧文件名也保留在上载控件上（可以看到悬停效果）

我从link那里获取了代码

//I added event handler for the file upload control to access the files properties.
document.addEventListener("DOMContentLoaded", init, false);

//To save an array of attachments 
var AttachmentArray = [];

//counter for attachment array
var arrCounter = 0;

//to make sure the error message for number of files will be shown only one time.
var filesCounterAlertStatus = false;

//un ordered list to keep attachments thumbnails
var ul = document.createElement('ul');
ul.className = ("thumb-Images");
ul.id = "imgList";

function init() {
    //add javascript handlers for the file upload event
    document.querySelector('#files').addEventListener('change', handleFileSelect, false);
}

//the handler for file upload event
function handleFileSelect(e) {
    //to make sure the user select file/files
    if (!e.target.files) return;

    //To obtaine a File reference
    var files = e.target.files;

    // Loop through the FileList and then to render image files as thumbnails.
    for (var i = 0, f; f = files[i]; i++) {

        //instantiate a FileReader object to read its contents into memory
        var fileReader = new FileReader();

        // Closure to capture the file information and apply validation.
        fileReader.onload = (function (readerEvt) {
            return function (e) {

                //Apply the validation rules for attachments upload
                ApplyFileValidationRules(readerEvt)

                //Render attachments thumbnails.
                RenderThumbnail(e, readerEvt);

                //Fill the array of attachment
                FillAttachmentArray(e, readerEvt)
            };
        })(f);

        // Read in the image file as a data URL.
        // readAsDataURL: The result property will contain the file/blob's data encoded as a data URL.
        // More info about Data URI scheme https://en.wikipedia.org/wiki/Data_URI_scheme
        fileReader.readAsDataURL(f);
    }
    document.getElementById('files').addEventListener('change', handleFileSelect, false);
}

//To remove attachment once user click on x button
jQuery(function ($) {
    $('div').on('click', '.img-wrap .close', function () {
        var id = $(this).closest('.img-wrap').find('img').data('id');

        //to remove the deleted item from array
        var elementPos = AttachmentArray.map(function (x) { return x.FileName; }).indexOf(id);
        if (elementPos !== -1) {
            AttachmentArray.splice(elementPos, 1);
        }

        //to remove image tag
        $(this).parent().find('img').not().remove();

        //to remove div tag that contain the image
        $(this).parent().find('div').not().remove();

        //to remove div tag that contain caption name
        $(this).parent().parent().find('div').not().remove();

        //to remove li tag
        var lis = document.querySelectorAll('#imgList li');
        for (var i = 0; li = lis[i]; i++) {
            if (li.innerHTML == "") {
                li.parentNode.removeChild(li);
            }
        }

    });
}
)

//Apply the validation rules for attachments upload
function ApplyFileValidationRules(readerEvt)
{
    //To check file type according to upload conditions
    if (CheckFileType(readerEvt.type) == false) {
        alert("The file (" + readerEvt.name + ") does not match the upload conditions, You can only upload jpg/png/gif files");
        e.preventDefault();
        return;
    }

    //To check file Size according to upload conditions
    if (CheckFileSize(readerEvt.size) == false) {
        alert("The file (" + readerEvt.name + ") does not match the upload conditions, The maximum file size for uploads should not exceed 300 KB");
        e.preventDefault();
        return;
    }

    //To check files count according to upload conditions
    if (CheckFilesCount(AttachmentArray) == false) {
        if (!filesCounterAlertStatus) {
            filesCounterAlertStatus = true;
            alert("You have added more than 10 files. According to upload conditions you can upload 10 files maximum");
        }
        e.preventDefault();
        return;
    }
}

//To check file type according to upload conditions
function CheckFileType(fileType) {
    if (fileType == "image/jpeg") {
        return true;
    }
    else if (fileType == "image/png") {
        return true;
    }
    else if (fileType == "image/gif") {
        return true;
    }
    else {
        return false;
    }
    return true;
}

//To check file Size according to upload conditions
function CheckFileSize(fileSize) {
    if (fileSize < 300000) {
        return true;
    }
    else {
        return false;
    }
    return true;
}

//To check files count according to upload conditions
function CheckFilesCount(AttachmentArray) {
    //Since AttachmentArray.length return the next available index in the array, 
    //I have used the loop to get the real length
    var len = 0;
    for (var i = 0; i < AttachmentArray.length; i++) {
        if (AttachmentArray[i] !== undefined) {
            len++;
        }
    }
    //To check the length does not exceed 10 files maximum
    if (len > 9) {
        return false;
    }
    else
    {
        return true;
    }
}

//Render attachments thumbnails.
function RenderThumbnail(e, readerEvt)
{
    var li = document.createElement('li');
    ul.appendChild(li);
    li.innerHTML = ['<div class="img-wrap"> <span class="close">&times;</span>' +
        '<img class="thumb" style="display:none;" src="', e.target.result, '" title="', escape(readerEvt.name), '" data-id="',
        readerEvt.name, '"/>' + '</div>'].join('');

    var div = document.createElement('div');
    div.className = "FileNameCaptionStyle";
    li.appendChild(div);
    div.innerHTML = [readerEvt.name].join('');
    document.getElementById('Filelist').insertBefore(ul, null);
}

//Fill the array of attachment
function FillAttachmentArray(e, readerEvt)
{
    AttachmentArray[arrCounter] =
    {
        AttachmentType: 1,
        ObjectType: 1,
        FileName: readerEvt.name,
        FileDescription: "Attachment",
        NoteText: "",
        MimeType: readerEvt.type,
        Content: e.target.result.split("base64,")[1],
        FileSizeInBytes: readerEvt.size,
    };
    arrCounter = arrCounter + 1;
}

/*Copied from bootstrap to handle input file multiple*/

.btn {
  display: inline-block;
  padding: 6px 12px;
  margin-bottom: 0;
  font-size: 14px;
  font-weight: normal;
  line-height: 1.42857143;
  text-align: center;
  white-space: nowrap;
  vertical-align: middle;
  cursor: pointer;
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
  background-image: none;
  border: 1px solid transparent;
  border-radius: 4px;
}

/*Also */

.btn-success {
  border: 1px solid #c5dbec;
  background: #D0E5F5;
  font-weight: bold;
  color: #2e6e9e;
}

/* This is copied from https://github.com/blueimp/jQuery-File-Upload/blob/master/css/jquery.fileupload.css */

.fileinput-button {
  position: relative;
  overflow: hidden;
}

.fileinput-button input {
  position: absolute;
  top: 0;
  right: 0;
  margin: 0;
  opacity: 0;
  -ms-filter: 'alpha(opacity=0)';
  font-size: 200px;
  direction: ltr;
  cursor: pointer;
}

.thumb {
  height: 80px;
  width: 100px;
  border: 1px solid #000;
}

ul.thumb-Images li {
  width: 120px;
  float: left;
  display: inline-block;
  vertical-align: top;
  height: 120px;
}

.img-wrap {
  position: relative;
  display: inline-block;
  font-size: 0;
}

.img-wrap .close {
  position: absolute;
  top: 2px;
  right: 2px;
  z-index: 100;
  background-color: #D0E5F5;
  padding: 5px 2px 2px;
  color: #000;
  font-weight: bolder;
  cursor: pointer;
  opacity: .5;
  font-size: 23px;
  line-height: 10px;
  border-radius: 50%;
}

.img-wrap:hover .close {
  opacity: 1;
  background-color: #ff0000;
}

.FileNameCaptionStyle {
  font-size: 12px;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<span class="btn btn-success fileinput-button">
  <span>Select Attachment</span>
  <input type="file" name="files[]" id="files" multiple accept="image/jpeg, image/png, image/gif,"><br />
</span>
<output id="Filelist"></output>

Answer 1

根据您的问题，您想操纵files property of <input> elements with type="file"。

一个FileList对象，列出每个选定的文件。此列表没有除非指定了multi属性，否则不止一个成员。

因此，它返回，因此即使您在<input type="file"/>上执行事件，它也仅返回选定的元素。您可以获取所选文件。获取所选文件

在jQuery

中

$("#files")[0].files

在纯js中

document.getElementById('files').files;

它返回所选元素的数组。 这些是您的上传文件按钮上显示的项目。

因此，您可以做些骇人听闻的事情，例如，您可以在title元素上设置自己的<input type="file">属性。浏览器不允许更改FileList，因此您需要使用技巧。这是一个示例片段。

var title = "";
$("#imgList>li").each(function(){
    title += `${$(this).find(".FileNameCaptionStyle").text()}\n`;
});
$("#files").attr("title", title);

//I added event handler for the file upload control to access the files properties.
document.addEventListener("DOMContentLoaded", init, false);

//To save an array of attachments 
var AttachmentArray = [];

//counter for attachment array
var arrCounter = 0;

//to make sure the error message for number of files will be shown only one time.
var filesCounterAlertStatus = false;

//un ordered list to keep attachments thumbnails
var ul = document.createElement('ul');
ul.className = ("thumb-Images");
ul.id = "imgList";

function init() {
    //add javascript handlers for the file upload event
    document.querySelector('#files').addEventListener('change', handleFileSelect, false);
}

//the handler for file upload event
function handleFileSelect(e) {
    //to make sure the user select file/files
    if (!e.target.files) return;

    //To obtaine a File reference
    var files = e.target.files;

    // Loop through the FileList and then to render image files as thumbnails.
    for (var i = 0, f; f = files[i]; i++) {

        //instantiate a FileReader object to read its contents into memory
        var fileReader = new FileReader();

        // Closure to capture the file information and apply validation.
        fileReader.onload = (function(readerEvt) {
            return function(e) {

                //Apply the validation rules for attachments upload
                ApplyFileValidationRules(readerEvt)

                //Render attachments thumbnails.
                RenderThumbnail(e, readerEvt);

                //Fill the array of attachment
                FillAttachmentArray(e, readerEvt)
            };
        })(f);

        // Read in the image file as a data URL.
        // readAsDataURL: The result property will contain the file/blob's data encoded as a data URL.
        // More info about Data URI scheme https://en.wikipedia.org/wiki/Data_URI_scheme
        fileReader.readAsDataURL(f);
    }
    document.getElementById('files').addEventListener('change', handleFileSelect, false);
}

//To remove attachment once user click on x button
jQuery(function($) {

    $('#Filelist').on('click', '.img-wrap .close', function() {
        var id = $(this).closest('.img-wrap').find('img').data('id');
        //to remove the deleted item from array
        var elementPos = AttachmentArray.map(function(x) {
            return x.FileName;
        }).indexOf(id);
        if (elementPos !== -1) {
            AttachmentArray.splice(elementPos, 1);
        }

        //to remove image tag
        $(this).parent().find('img').not().remove();

        //to remove div tag that contain the image
        $(this).parent().find('div').not().remove();

        //to remove div tag that contain caption name
        $(this).parent().parent().find('div').not().remove();

        //to remove li tag
        var lis = document.querySelectorAll('#imgList li');
        for (var i = 0; li = lis[i]; i++) {
            if (li.innerHTML == "") {
                li.parentNode.removeChild(li);
            }
        }
        changeTitle();
    });
});

//Apply the validation rules for attachments upload
function ApplyFileValidationRules(readerEvt) {
    //To check file type according to upload conditions
    if (CheckFileType(readerEvt.type) == false) {
        alert("The file (" + readerEvt.name + ") does not match the upload conditions, You can only upload jpg/png/gif files");
        e.preventDefault();
        return;
    }

    //To check file Size according to upload conditions
    if (CheckFileSize(readerEvt.size) == false) {
        alert("The file (" + readerEvt.name + ") does not match the upload conditions, The maximum file size for uploads should not exceed 300 KB");
        e.preventDefault();
        return;
    }

    //To check files count according to upload conditions
    if (CheckFilesCount(AttachmentArray) == false) {
        if (!filesCounterAlertStatus) {
            filesCounterAlertStatus = true;
            alert("You have added more than 10 files. According to upload conditions you can upload 10 files maximum");
        }
        e.preventDefault();
        return;
    }
}

//To check file type according to upload conditions
function CheckFileType(fileType) {
    if (fileType == "image/jpeg") {
        return true;
    } else if (fileType == "image/png") {
        return true;
    } else if (fileType == "image/gif") {
        return true;
    } else {
        return false;
    }
    return true;
}

//To check file Size according to upload conditions
function CheckFileSize(fileSize) {
    if (fileSize < 300000) {
        return true;
    } else {
        return false;
    }
    return true;
}

//To check files count according to upload conditions
function CheckFilesCount(AttachmentArray) {
    //Since AttachmentArray.length return the next available index in the array, 
    //I have used the loop to get the real length
    var len = 0;
    for (var i = 0; i < AttachmentArray.length; i++) {
        if (AttachmentArray[i] !== undefined) {
            len++;
        }
    }
    //To check the length does not exceed 10 files maximum
    if (len > 9) {
        return false;
    } else {
        return true;
    }
}

//Render attachments thumbnails.
function RenderThumbnail(e, readerEvt) {
    var li = document.createElement('li');
    ul.appendChild(li);
    li.innerHTML = ['<div class="img-wrap"> <span class="close">&times;</span>' +
        '<img class="thumb" style="display:none;" src="', e.target.result, '" title="', escape(readerEvt.name), '" data-id="',
        readerEvt.name, '"/>' + '</div>'
    ].join('');

    var div = document.createElement('div');
    div.className = "FileNameCaptionStyle";
    li.appendChild(div);
    div.innerHTML = [readerEvt.name].join('');
    document.getElementById('Filelist').insertBefore(ul, null);
    changeTitle();
}

//Fill the array of attachment
function FillAttachmentArray(e, readerEvt) {
    AttachmentArray[arrCounter] = {
        AttachmentType: 1,
        ObjectType: 1,
        FileName: readerEvt.name,
        FileDescription: "Attachment",
        NoteText: "",
        MimeType: readerEvt.type,
        Content: e.target.result.split("base64,")[1],
        FileSizeInBytes: readerEvt.size,
    };
    arrCounter = arrCounter + 1;
}

function changeTitle() {
    var title = "";
    $("#imgList>li").each(function() {
        title += `${$(this).find(".FileNameCaptionStyle").text()}\n`;
    });
    $("#files").attr("title", title);
}

/*Copied from bootstrap to handle input file multiple*/
.btn {
    display: inline - block;
    padding: 6 px 12 px;
    margin - bottom: 0;
    font - size: 14 px;
    font - weight: normal;
    line - height: 1.42857143;
    text - align: center;
    white - space: nowrap;
    vertical - align: middle;
    cursor: pointer; -
    webkit - user - select: none; -
    moz - user - select: none; -
    ms - user - select: none;
    user - select: none;
    background - image: none;
    border: 1 px solid transparent;
    border - radius: 4 px;
}

/*Also */

.btn - success {
    border: 1 px solid# c5dbec;
    background: #D0E5F5;
    font - weight: bold;
    color: #2e6e9e;
}

/* This is copied from https://github.com/blueimp/jQuery-File-Upload/blob/master/css/jquery.fileupload.css */

.fileinput-button {
  position: relative;
  overflow: hidden;
}

.fileinput-button input {
  position: absolute;
  top: 0;
  right: 0;
  margin: 0;
  opacity: 0;
  -ms-filter: 'alpha(opacity= 0)
';
font - size: 200 px;
direction: ltr;
cursor: pointer;
}

.thumb {
    height: 80 px;
    width: 100 px;
    border: 1 px solid #000;
}

ul.thumb-Images li {
  width: 120px;
  float: left;
  display: inline-block;
  vertical-align: top;
  height: 120px;
}

.img-wrap {
  position: relative;
  display: inline-block;
  font-size: 0;
}

.img-wrap .close {
  position: absolute;
  top: 2px;
  right: 2px;
  z-index: 100;
  background-color: # D0E5F5;
    padding: 5 px 2 px 2 px;
    color: #000;
  font-weight: bolder;
  cursor: pointer;
  opacity: .5;
  font-size: 23px;
  line-height: 10px;
  border-radius: 50%;
}

.img-wrap:hover .close {
  opacity: 1;
  background-color: # ff0000;
}

.FileNameCaptionStyle {
    font - size: 12 px;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
<span class="btn btn-success fileinput-button">
    <span>Select Attachment</span>
    <input type="file" name="files[]" id="files" multiple accept="image/jpeg, image/png, image/gif,"><br />
</span>
<output id="Filelist"></output>

Answer 2

您所描述的只是html文件输入行为。它与jQuery无关。文件输入将在每次交互时更新其value和files属性。也就是说，如果您：

点击输入
选择5个文件
再次单击输入
在对话框中单击“取消”（或按 esc 键）

您输入的文件的value属性将有一个空白的FileList和一个空白的files，因为您在上一次交互时选择了一个空白。

如果要保留所有选定文件的运行清单，并允许用户删除和添加文件，则必须将文件字段仅作为一次性输入，而不是真理的来源。您侦听输入的更改，获取传入的files数据并将其添加到本地文件数组中，然后必须确保在每次选择后都要重置输入。

Here's a codesandbox上的工作示例显示了我的意思。

在这种情况下，当您保存表单数据时，将不会从文件输入中读取内容。您将忽略文件输入，并从本地变量手动添加文件。

要注意的另一件事是文件输入的files属性是只读的。如果您想清除它，只需将value设置为null，即可解决问题。

旧文件会从jQuery文件上传控件中删除

2 个答案: