Integrating input[type=file] with the Filesystem API
Let's say you have a photo editing app and you'd like users to be able to drag in hundreds of photos and copy them into your app. Ok, what do you do?
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.
To learn more about the HTML5 Filesystem API, see Exploring the Filesystem APIs.