mouseJoint box2dweb doesn't work - mouse

Question

I am trying to catch object with mouse using mousejoint. As I am a fool I've stolen the code. But it isnt working or me.
I am getting this errors:
Uncaught TypeError: Object #< ba > has no method 'IsActive' Box2dWeb-2.1.a.3.min.js:236
Uncaught TypeError: Object #< ba > has no method 'SetAwake' Box2dWeb-2.1.a.3.min.js:223
here is the code:
var def = new b2MouseJointDef();
def.bodyA = ground;
def.bodyB = body;
def.target = p;
def.collideConnected = true;
def.maxForce = 1000 * body.GetMass();
def.dampingRatio = 0;
mouse_joint = world.CreateJoint(def);
body.SetAwake(true);
And this is the body
function createBox(world, x, y, width, height, options) {
options = $.extend(true, {
'density' : 1.0 ,
'friction' : 1.0 ,
'restitution' : 0.5 ,
'linearDamping' : 0.0 ,
'angularDamping' : 0.0 ,
'type' : b2Body.b2_dynamicBody
}, options);
var body_def = new b2BodyDef();
var fix_def = new b2FixtureDef();
fix_def.density = options.density;
fix_def.friction = options.friction;
fix_def.restitution = options.restitution;
fix_def.shape = new b2PolygonShape();
fix_def.shape.SetAsBox( width , height );
body_def.position.Set(x , y);
body_def.linearDamping = options.linearDamping;
body_def.angularDamping = options.angularDamping;
body_def.type = options.type;
body_def.userData = options.user_data;
var b = world.CreateBody( body_def );
var f = b.CreateFixture(fix_def);
return b;
}
Maybe someone can help?
Falk

Answer 1

I can answer half of the question:
if I set up the ground with
ground = createBox(world, 4, 1, 4 , 0.5, {type : b2Body.b2_staticBody});
instead with this function:
var bodyDef = new b2BodyDef();
var fixDef = new b2FixtureDef();
fixDef.density = 1.0;
fixDef.friction = 1.0;
fixDef.restitution = 0.5;
fixDef.shape = new b2PolygonShape;
//mention half the sizes
fixDef.shape.SetAsBox(4.00 , .5);
//set the position of the center
bodyDef.position.Set(4.10 , 1);
return world.CreateBody(bodyDef).CreateFixture(fixDef);
then it is working. But why?