Using Promises to wait for UI actions

gistfile1.txt

function waitForLogin(message) {
	return new Promise(function(resolve) {
		if (alreadyLoggedIn) {
			resolve();
		} else {
			if (message) {
				showMessage(message);
			}
			addEventListener('logged-in', resolve);
		}
	});
}

// Scattered throughout the code.
waitForLogin("Login in to do something.").then(doSomething);
waitForLogin("Login to do something else.").then(doSomethingElse);
waitForLogin().then(doSomethingWithoutPrompting);

test.js

// test