gistfile1.js

body1 = new Body(physics, { color:"red", x: 15, y: 12 }).body;
body2 = new Body(physics, { image: img, x: 25, y: 12 }).body;
def = new Box2D.Dynamics.Joints.b2PulleyJointDef();

def.Initialize(body1, body2,
               new b2Vec2(13,0),
               new b2Vec2(25,0),
               body1.GetWorldCenter(),
               body2.GetWorldCenter(),
               1);
var joint = world.CreateJoint(def);