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Drag and drop a folder onto Chrome now available

As web apps evolve, you might have found it handy to let users drag and drop files from the desktop onto the browser to edit, upload, share, etc. But unfortunately, we’ve been unable to drag and drop folders onto web pages. Luckily, beginning with Chrome 21, this issue will be addressed (already available in the Chrome dev channel).

Passing multiple files with drag and drop

Let’s look at a code sample of existing drag and drop.

<div id=”dropzone”></div>

var dropzone = document.getElementById('dropzone');
dropzone.ondrop = function(e) {
  var length = e.dataTransfer.files.length;
  for (var i = 0; i < length; i++) {
    var file = e.dataTransfer.files[i];
    ... // do whatever you want
  }
};

In this example, you can actually drag and drop a file or files from the desktop to your browser, but when you try to pass a folder, notice that it will be either rejected or treated as a File object resulting in a failure.

How to handle dropped folders

Chrome 21 allows you to drop a folder or multiple folders into the browser window. To handle these, you need to change the way you handle dropped objects.

<div id=”dropzone”></div>

var dropzone = document.getElementById('dropzone');
dropzone.ondrop = function(e) {
  var length = e.dataTransfer.items.length;
  for (var i = 0; i < length; i++) {
    var entry = e.dataTransfer.items[i].webkitGetAsEntry();
    if (entry.isFile) {
      ... // do whatever you want
    } else if (entry.isDirectory) {
      ... // do whatever you want
    }
  }
};

Notice that a big difference here is that you can treat a dropped object as Entry (FileEntry or DirectoryEntry) by using new function called getAsEntry (webkitGetAsEntry).
After obtaining access to the Entry object, you can use standard file handling methods that were introduced in the FileSystem API specification. For example, this example shows how you can detect if a dropped object is a file or a directory by examining the .isFile (or the .isDirectory) field.

For further information regarding the FileSystem API, read Exploring the FileSystem APIs, regarding new drag and drop capability, read this document. Of course, these features are open standards or are waiting to become one soon.

 Integrating input[type="file"] with the Filesystem API

 - http://updates.html5rocks.com/tag/file-access

: http://html5-demos.appspot.com/static/dnd/all_types_of_import.html

In a recent post, Eiji Kitamura highlighted a subtle, yet powerful new feature in the drag and drop APIs; the ability to drag in folders and retrieve them as HTML5 Filesystem API FileEntry and DirectoryEntry objects (done by accessing a new method on the DataTransferItem, .webkitGetAsEntry()).

What's remarkably cool about the .webkitGetAsEntry() extension is how elegant it makes importing files and entire folders. Once you have a FileEntry or DirectoryEntry from a drop event, it's a matter of using the Filesystem API's copyTo() to get it imported into your app.

An example of copying multiple dropped folders over to the filesystem:

var fs = null; // Cache filesystem for later.

// Not shown: setup drag and drop event listeners.
function onDrop(e) {
  e.preventDefault();
  e.stopPropagation();

  var items = e.dataTransfer.items;

  for (var i = 0, item; item = items[i]; ++i) { 
    var entry = item.webkitGetAsEntry();

    // Folder? Copy the DirectoryEntry over to our local filesystem.
    if (entry.isDirectory) {
      entry.copyTo(fs.root, null, function(copiedEntry) {
        // ...
      }, onError);
    }
  }
}

window.webkitRequestFileSystem(TEMPORARY, 1024 * 1204, function(fileSystem) {
  fs = fileSystem;
}, function(e) {
  console.log('Error', e);
});

Very nice! Again, the simplicity comes from integrating DnD with the Filesystem API calls.

Taking this one step further, we also have the ability to drag and drop a folder and/or files onto a normal <input type="file">, then access the entries as Filesystem directory or file entries. That is done through .webkitEntries:

<input type="file" multiple>

function onChange(e) {
  e.stopPropagation();
  e.preventDefault();

  var entries = e.target.webkitEntries; // Get all dropped items as FS API entries.

  [].forEach.call(entries, function(entry) {

    // Copy the entry into our local filesystem.
    entry.copyTo(fs.root, null, function(copiedEntry) {
      ...
    }, onError);

  });
}

document.querySelector('input[type="file"]').addEventListener('change', onChange);

I've put together a photo gallery demo to demonstrate these different techniques for importing files/folders.

Launch Demo

To learn more about the HTML5 Filesystem API, see Exploring the Filesystem APIs.

어떤 일을 달성하기로 결심했으면 그 어떤 지겨움과 혐오감도 불사하고 완수하라.

고단한 일을 해낸 데서 오는 자신감은 실로 엄청나다.

- 아놀드 베넷