1j01

function blob_to_buffer(blob, callback) {
	const file_reader = new FileReader()

	file_reader.addEventListener("loadend", event => {
		if (file_reader.error) {
			callback(file_reader.error)
		} else {
			callback(null, new Buffer(file_reader.result))
		}
	}, false)

1j01

// first setup our stacks of history states
// (const refers to the reference to the arrays, but they arrays themselves are mutable)
const undos = [];
const redos = [];

// undo and redo are symmetrical operations, so they *could* be factored to use an "undoOrRedo" / "stepHistory" function that takes two stacks as arguments, but it might be clearer as two functions

const undo = () => {
	if (undos.length < 1) { return false; }