object-event system with JS-like syntax

gistfile1.txt

class Player {
    constructor( hp ) {
        this.hp = hp;
        this.isAlive = true;
    }

    damage( att ) {
        this.hp = Math.min( 0, this.hp - att );
        this.isAlive = false;
    }
}

var player = new Player( 10 );
var ui = new PlayerUI();
var screen = new Screen();

// hang events off existing methods
player.damage := () {
    ui.show( this.getHealth() );
}
player.damage := () {
    screen.flash( 'red' );
}

screen.draw := ( gfx ) {
    ui.draw( gfx );
}

// a regular method call
player.damage( 5 )