Hello Folks!

Imagine that you are working on an application for a traveling agency that needs to have several files attached to a single reservation. In this case it can be for one traveler or several ones which will lead to upload information into the database such as travel insurance, passport Id, driver's license, flight and hotel Information among others.

Since it is important to save time and accomplish tasks in a timely manner, we want to share with you this guide on how you can upload multiple files at once and be more efficient in the work you do.

Just follow these simple steps:

1. Create new Object in Builder with at least one field of type File

2. Create a new page with the options selected below

3. Insert the following code in the API & Code section of the APP (Javascript Tab):

var ASYNC_URL =
  'https://cdnjs.cloudflare.com/ajax/libs/async/1.5.0/async.min.js';
// Replace your Knack APP info
var headers = {
  'X-Knack-Application-ID': 'XXXXXXXXXXX',
  'X-Knack-REST-API-Key': 'YYYYYYYYYYYYYYYY'
};
var uploadFile = function (type, filename, blob, success, error) {
  //https://api.knackhq.com/v1/applications/app_id/assets/file/upload
  success = success || function () {};
  error = error || function () {};
  type = type || 'image';
  // Required
  var fd = new FormData();
  // Add files
  if (filename) {
    fd.append('files', blob, filename);
  } else {
    fd.append('files', blob);
  }
  // Return a promise
  return $.ajax({
    type: 'POST',
    url:
      Knack.api_url +
      '/v1/applications/' +
      headers['X-Knack-Application-ID'] +
      '/assets/' +
      type +
      '/upload',
    headers,
    data: fd,
    processData: false,
    contentType: false,
    success,
    error
  });
};
var createRecord = function (fileId) {
  return $.ajax({
    // Replace object id
    url: Knack.api_url + '/v1/objects/object_XX/records',
    type: 'POST',
    headers,
    data: {
      field_XXX: fileId     // Replace file field_id
    }
  });
};
var dataURItoBlob = function (dataURI) {
  var byteString;
  if (dataURI.split(',')[0].indexOf('base64') >= 0) {
    byteString = atob(dataURI.split(',')[1]);
  } else {
    byteString = unescape(dataURI.split(',')[1]);
  }
  // separate out the mime component
  var mimeString = dataURI.split(',')[0].split(':')[1].split(';')[0];
  // write the bytes of the string to a typed array
  var ia = new Uint8Array(byteString.length);
  for (var i = 0; i < byteString.length; i++) {
    ia[i] = byteString.charCodeAt(i);
  }
  return new Blob([ia], { type: mimeString });
};
// Replace your scene id
$(document).on('knack-page-render.scene_XXX', function (e, view) {
  var viewForm = 'view_XXX';  // Replace your form view id
  // Replace file field_id
  $(
    '<div class="kn-input kn-input-file">' +
      '<label for="field_XXX" class="knack-input-label"><span class="kn-input-label">Files to upload</span></label>' +
      '<input type="file" id="fileselect" name="fileselect[]" multiple="multiple" />' +
      '<div id="filedrag">or drop files here</div>' +
      '<div id="messages"></div>' +
      '</div>'
  ).insertAfter('#' + viewForm + ' .kn-form-group-1');
  var $submitInput = $('#' + viewForm + ' .kn-submit button[type=submit]');
  // Prevent submit action
  $submitInput.hide();
  LazyLoad.js([ASYNC_URL], function () {
    if (window.File && window.FileList && window.FileReader) {
      initialize();
    }
    function $id(id) {
      return document.getElementById(id);
    }
    function output(msg) {
      var m = $id('messages');
      m.innerHTML = msg + m.innerHTML;
    }
    function initialize() {
      window.files = [];
      var fileselect = $id('fileselect');
      var filedrag = $id('filedrag');
      // file select
      fileselect.addEventListener('change', FileSelectHandler, false);
      // file drop
      filedrag.addEventListener('dragover', FileDragHover, false);
      filedrag.addEventListener('dragleave', FileDragHover, false);
      filedrag.addEventListener('drop', FileSelectHandler, false);
      filedrag.style.display = 'block';
      // handle submit action
      $submitInput.on('click', function (event) {
        event.preventDefault();
        if (!files.length) {
          alert('Error, they have not been selected files');
          return;
        }
        Knack.showSpinner();
        async.each(
          files,
          function (file, next) {
            var fileReader = new FileReader();
            fileReader.onloadend = function (e) {
              var blob = dataURItoBlob(fileReader.result);
              uploadFile('file', file.name, blob, function (record) {
                createRecord(record.id)
                  .done(function () {
                    next();
                  })
                  .fail(next);
              });
            };
            fileReader.readAsDataURL(file);
          },
          function (err) {
            if (err) {
              alert('Internal error, please consult with your administrator.');
            }
            alert('All files were created successfully');
            // This reloads the page (it is optional)
            location.reload();
          }
        );
      });
      function FileDragHover(e) {
        e.stopPropagation();
        e.preventDefault();
        e.target.className = e.type == 'dragover' ? 'hover' : '';
      }
      // file selection
      function FileSelectHandler(e) {
        // cancel event and hover styling
        FileDragHover(e);
        // fetch FileList object
        var _files = e.target.files || e.dataTransfer.files;
        // process all File objects
        for (var i = 0, f; (f = _files[i]); i++) {
          files.push(f);
          showInformation(f, files.length);
        }
        handleRemoveFileEvents();
        // Allow submit
        $submitInput.show();
      }
      function showInformation(file, index) {
        output(
          '<p>' +
            'File information: <strong> ' +
            file.name +
            '</strong> type: <strong> ' +
            file.type +
            '</strong> size: <strong> ' +
            file.size +
            '</strong> bytes' +
            '&nbsp;&nbsp;&nbsp;' +
            '<a href="#" class="removeFile" data-index="' +
            index +
            '">remove</a>' +
            '</p>'
        );
      }
      function refreshInformation() {
        var m = $id('messages');
        m.innerHTML = '';
        for (var i = 0, f; (f = files[i]); i++) {
          showInformation(f, i + 1);
        }
        handleRemoveFileEvents();
      }
      function handleRemoveFileEvents() {
        $('.removeFile').on('click', function (e) {
          e.preventDefault();
          var $target = $(e.target);
          var index = $target.attr('data-index');
          files.splice(index - 1, 1);
          // Clear all
          $('.removeFile').off();
          // Capture again
          refreshInformation();
        });
      }
    }
  });
});

4. Insert the following code in the API & Code section of the APP (CSS Tab):

/* Replace your form view id */
#view_XXX form .kn-form-group-1 {
  display: none;
}
#filedrag
{
  min-height: 100px;
  display: none;
  font-weight: bold;
  text-align: center;
  padding: 1em 0;
  margin: 1em 0;
  color: #555;
  border: 2px dashed #555;
  border-radius: 7px;
  cursor: default;
  height: 50px;
  padding-top: 45px;
}
#filedrag.hover
{
  color: #f00;
  border-color: #f00;
  border-style: solid;
  box-shadow: inset 0 3px 4px #888;
}
#messages {
  margin-top: 15px;
}
#messages p {
  margin-bottom: 2px !important;
}

5. Implementation demo:

Enter this site and watch how it works: https://soluntech.knack.com/test#multifile-upload/

If you found this helpful, please share it with your colleagues!

Let's Make IT Happen!

A Simple Guide on how to Upload Multiples Files in Knack! - (Object Based)