Javascript Polling with Promises

poll.js

var Promise = require('bluebird');

/**
 * Periodically poll a signal function until either it returns true or a timeout is reached.
 *
 * @param signal function that returns true when the polled operation is complete
 * @param interval time interval between polls in milliseconds
 * @param timeout period of time before giving up on polling
 * @returns true if the signal function returned true, false if the operation timed out
 */
function poll(signal, interval, timeout) {
    function pollRecursive() {
        return signal() ? Promise.resolve(true) : Promise.delay(interval).then(pollRecursive);
    }

    return pollRecursive()
        .cancellable()
        .timeout(timeout)
        .catch(Promise.TimeoutError, Promise.CancellationError, function () {
            return false;
        });
}

/**
 * Every 2 seconds, call a signal function that returns true 25% of the time. Timeout after 10 seconds.
 */
poll(randomSignal, 2000, 10000).then(console.log);

function randomSignal() {
    var r = Math.random() <= 0.25;
    console.log(r ? "Complete" : "Not complete");
    return r;
}

@formula1, thanks for this!