EventObserver

EventObserver is a way to handle DOM events like Promises.

To learn more about EventObserver, visit the documentation.

Demo

Listen to every English-alphabetical keystroke until x is pressed.

// log English-alphabetical keyCodes until 'x' is pressed

var output = document.getElementById('output');

document.on('keydown').map(function (event) {
	return event.keyCode;
}).filter(function (keyCode) {
	return keyCode >= 65 && keyCode <= 90;
}).then(function (keyCode) {
	output.innerHTML = keyCode === 88 ? 'Fin' : keyCode;
}).until(function (keyCode) {
	return keyCode === 88;
});

Output

ready

To learn more about EventObserver, visit the documentation.