Multiplexed streams compete

compete.js

module.exports = compete;

/**
 * Filter function to determine which of all multiplexed streams
 * is currently winning.
 * TODO: change this so that multiple streams can be winners, but
 *     don't use an array of winners.  Perhaps inject another function?
 */
function compete (identify, compare) {
    var winner, wid;
    return function (value) {
        var id = identify(value);
        if (id === wid || compare(value, winner) >= 0) {
            winner = value;
            wid = id;
        }
        return winner == value;
    };
}