[javascript] How to use FormData for AJAX file upload?

This is my HTML which I'm generating dynamically using drag and drop functionality.

<form method="POST" id="contact" name="13" class="form-horizontal wpc_contact" novalidate="novalidate" enctype="multipart/form-data">
<fieldset>
    <div id="legend" class="">
        <legend class="">file demoe 1</legend>
        <div id="alert-message" class="alert hidden"></div>
    </div>

    <div class="control-group">
        <!-- Text input-->
        <label class="control-label" for="input01">Text input</label>
        <div class="controls">
            <input type="text" placeholder="placeholder" class="input-xlarge" name="name">
            <p class="help-block" style="display:none;">text_input</p>
        </div>
        <div class="control-group">  </div>
        <label class="control-label">File Button</label>

        <!-- File Upload --> 
        <div class="controls">
            <input class="input-file" id="fileInput" type="file" name="file">
        </div>
    </div>
    <div class="control-group">    

        <!-- Button --> 
        <div class="controls">
            <button class="btn btn-success">Button</button>
        </div>
    </div>
</fieldset>
</form> 

This is my JavaScript code:

<script>
    $('.wpc_contact').submit(function(event){
        var formname = $('.wpc_contact').attr('name');
        var form = $('.wpc_contact').serialize();               
        var FormData = new FormData($(form)[1]);

        $.ajax({
            url : '<?php echo plugins_url(); ?>'+'/wpc-contact-form/resources/js/tinymce.php',
            data : {form:form,formname:formname,ipadd:ipadd,FormData:FormData},
            type : 'POST',
            processData: false,
            contentType: false,
            success : function(data){
            alert(data); 
            }
        });
   }

View:
<label class="btn btn-info btn-file">
Import <input type="file" style="display: none;">
</label>
<Script>
$(document).ready(function () {
                $(document).on('change', ':file', function () {
                    var fileUpload = $(this).get(0);
                    var files = fileUpload.files;
                    var bid = 0;
                    if (files.length != 0) {
                        var data = new FormData();
                        for (var i = 0; i < files.length ; i++) {
                            data.append(files[i].name, files[i]);
                        }
                        $.ajax({
                            xhr: function () {
                                var xhr = $.ajaxSettings.xhr();
                                xhr.upload.onprogress = function (e) {
                                    console.log(Math.floor(e.loaded / e.total * 100) + '%');
                                };
                                return xhr;
                            },
                            contentType: false,
                            processData: false,
                            type: 'POST',
                            data: data,
                            url: '/ControllerX/' + bid,
                            success: function (response) {
                                location.href = 'xxx/Index/';
                            }
                        });
                    }
                });
            });
</Script>
Controller:
[HttpPost]
        public ActionResult ControllerX(string id)
        {
            var files = Request.Form.Files;
...

Better to use the native javascript to find the element by id like: document.getElementById("yourFormElementID").

$.ajax( {
      url: "http://yourlocationtopost/",
      type: 'POST',
      data: new FormData(document.getElementById("yourFormElementID")),
      processData: false,
      contentType: false
    } ).done(function(d) {
           console.log('done');
    });

I can't add a comment above as I do not have enough reputation, but the above answer was nearly perfect for me, except I had to add

type: "POST"

to the .ajax call. I was scratching my head for a few minutes trying to figure out what I had done wrong, that's all it needed and works a treat. So this is the whole snippet:

Full credit to the answer above me, this is just a small tweak to that. This is just in case anyone else gets stuck and can't see the obvious.

  $.ajax({
    url: 'Your url here',
    data: formData,
    type: "POST", //ADDED THIS LINE
    // THIS MUST BE DONE FOR FILE UPLOADING
    contentType: false,
    processData: false,
    // ... Other options like success and etc
})

<form id="upload_form" enctype="multipart/form-data">

jQuery with CodeIgniter file upload:

var formData = new FormData($('#upload_form')[0]);

formData.append('tax_file', $('input[type=file]')[0].files[0]);

$.ajax({
    type: "POST",
    url: base_url + "member/upload/",
    data: formData,
    //use contentType, processData for sure.
    contentType: false,
    processData: false,
    beforeSend: function() {
        $('.modal .ajax_data').prepend('<img src="' +
            base_url +
            '"asset/images/ajax-loader.gif" />');
        //$(".modal .ajax_data").html("<pre>Hold on...</pre>");
        $(".modal").modal("show");
    },
    success: function(msg) {
        $(".modal .ajax_data").html("<pre>" + msg +
            "</pre>");
        $('#close').hide();
    },
    error: function() {
        $(".modal .ajax_data").html(
            "<pre>Sorry! Couldn't process your request.</pre>"
        ); // 
        $('#done').hide();
    }
});

you can use.

var form = $('form')[0]; 
var formData = new FormData(form);     
formData.append('tax_file', $('input[type=file]')[0].files[0]);

or

var formData = new FormData($('#upload_form')[0]);
formData.append('tax_file', $('input[type=file]')[0].files[0]); 

Both will work.

$('#form-withdraw').submit(function(event) {

    //prevent the form from submitting by default
    event.preventDefault();



    var formData = new FormData($(this)[0]);

    $.ajax({
        url: 'function/ajax/topup.php',
        type: 'POST',
        data: formData,
        async: false,
        cache: false,
        contentType: false,
        processData: false,
        success: function (returndata) {
          if(returndata == 'success')
          {
            swal({
              title: "Great",
              text: "Your Form has Been Transfer, We will comfirm the amount you reload in 3 hours",
              type: "success",
              showCancelButton: false,
              confirmButtonColor: "#DD6B55",
              confirmButtonText: "OK",
              closeOnConfirm: false
            },
            function(){
              window.location.href = '/transaction.php';
            });
          }

          else if(returndata == 'Offline')
          {
              sweetAlert("Offline", "Please use other payment method", "error");
          }
        }
    });



}); 

$(document).ready(function () {
    $(".submit_btn").click(function (event) {
        event.preventDefault();
        var form = $('#fileUploadForm')[0];
        var data = new FormData(form);
        data.append("CustomField", "This is some extra data, testing");
        $("#btnSubmit").prop("disabled", true);
        $.ajax({
            type: "POST",
            enctype: 'multipart/form-data',
            url: "upload.php",
            data: data,
            processData: false,
            contentType: false,
            cache: false,
            timeout: 600000,
            success: function (data) {
                console.log();
            },
        });
    });
});

Good morning.

I was have the same problem with upload of multiple images. Solution was more simple than I had imagined: include [] in the name field.

<input type="file" name="files[]" multiple>

I did not make any modification on FormData.

Actually The documentation shows that you can use XMLHttpRequest().send() to simply send multiform data in case jquery sucks