Playing with JS Syntax.

fileResizer.js

function fileResizer(fileRepository, fileStore, renderThumbnail) {

	function listen(event) {
		event.data.files.forEach(function(id) {
							getFileContents(id, renderThumbnailToStore);
						});
	}

	function getFileContents(id, next) {
		fileRepository.getById(id, function(err, file) {
			fileStore.get(file.contentsId, function(err, stream) {
				if (err) {
					return next(err);
				}
				next(err, { id: file.id, filename: file.filename, stream: stream });
			});
		});
	}

	function renderThumbnailToStore(err, fileDetails) {
		function resize(thumbnail) {
			var outputStream = fileStore.stream(thumbnail.size + '_' + fileDetails.id.toString() + '_' + fileDetails.filename);
			renderThumbnail({ x: thumbnail.x, y: thumbnail.y, inputStream: fileDetails.stream, outputStream: outputStream });
		}

		resize({ x: 100, y: 100, size: 'small' });
		resize({ x: 250, y: 250, size: 'medium' });
		resize({ x: 500, y: 500, size: 'large' });
	}

	return Object.freeze({ listen: listen });
}
 
module.exports = fileResizer;