AJAX single file upload wordpress

<form method="post" enctype="multipart/form-data">

   <div class="form-group">

      <label>Choose File:</label>

      <input type="file" id="file" />

   </div>

</form>

 

<script>

    var ajaxurl = "<?php echo admin_url('admin-ajax.php'); ?>";

    jQuery(function($) {

        $('body').on('change', '#file', function() {

            var file_data = $(this).prop('files')[0];

            var form_data = new FormData();

            form_data.append('file', file_data);

            form_data.append('action', 'file_upload');

 

            jQuery.ajax({

                url: ajaxurl,

                type: 'POST',

                contentType: false,

                processData: false,

                data: form_data,

                success: function (response) {

                    alert('File uploaded successfully');

                }

            });

        });

    });

</script>

 

functions.php--

add_action( 'wp_ajax_file_upload', 'file_upload_callback' );

add_action( 'wp_ajax_nopriv_file_upload', 'file_upload_callback' );

 

function file_upload_callback() {

   $upload = wp_upload_bits($_FILES["file"]["name"], null, file_get_contents($_FILES["file"]["tmp_name"]));

   wp_die();

}