Upload folder and all its content in JavaScript

How do I upload the content of a folder using JavaScript (client side)? The FileSystem API has not been adopted by browsers other than Chrome; I only get a File item with the name of the folder.

It should be possible, because Google Drive allows to drop a folder and all the content (folders and files) will be uploaded automatically.

It seems that Chrome and Firefox supports part of the filesystem API, but are not oficially supported.

This allows you to drop a folder and read all the content, here's the code i use on my app.

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

        // if directory support is available
        if(e.dataTransfer && e.dataTransfer.items)
        {
            var items = e.dataTransfer.items;
            for (var i=0; i<items.length; i++) {
                var item = items[i].webkitGetAsEntry();

                if (item) {
                  addDirectory(item);
                }
            }
            return;
        }

        // Fallback
        var files = e.target.files || e.dataTransfer.files;
        if (!files.length)
        {
            alert('File type not accepted');
            return;
        }

        processFile(files);
    }

    function addDirectory(item) {
        var _this = this;
        if (item.isDirectory) {
            var directoryReader = item.createReader();
            directoryReader.readEntries(function(entries) {
            entries.forEach(function(entry) {
                    _this.addDirectory(entry);
                });
            });
        } else {
            item.file(function(file){
                processFile([file],0);
            });
        }
    },