中介者模式

几个对象之间不直接通话，而是通过一个中介者进行通信，从而促进形成宋耦合。

例子： http://www.jspatterns.com/book/7/mediator.html

// player constructor
function Player(name) {
    this.points = 0;
    this.name = name;
}
// play method
Player.prototype.play = function () {
    this.points += 1;
    mediator.played();
};

// the scoreboard object
var scoreboard = {

    // HTML element to be updated
    element: document.getElementById('results'),

    // update the score display
    update: function (score) {

        var i, msg = '';
        for (i in score) {
            if (score.hasOwnProperty(i)) {
                msg += '<p><strong>' + i + '<\/strong>: ';
                msg += score[i];
                msg += '<\/p>';
            }
        }
        this.element.innerHTML = msg;
    }
};


var mediator = {

    // all the players
    players: {},

    //
    setup: function () {
        var players = this.players;
        players.home = new Player('Home');
        players.guest = new Player('Guest');

    },

    // someone plays, update the score
    played: function () {
        var players = this.players,
                score = {
                    Home: players.home.points,
                    Guest: players.guest.points
                };

        scoreboard.update(score);
    },

    // handle user interactions
    keypress: function (e) {
        e = e || window.event; // IE
        if (e.which === 49) { // key "1"
            mediator.players.home.play();
            return;
        }
        if (e.which === 48) { // key "0"
            mediator.players.guest.play();
            return;
        }
    }
};


// go!
mediator.setup();
window.onkeypress = mediator.keypress;

// game over in 30 seconds
setTimeout(function () {
    window.onkeypress = null;
    alert('Game over!');
}, 30000);