Weld joint in box2d in javascript

Weld joint in box2d
The weld joint can be used to join to bodies tightly at a common point. Here is an example

A weld joint is created like this

//create distance joint between b and c
var joint_def = new b2WeldJointDef();
joint_def.bodyA = b;
joint_def.bodyB = c;

//connect the centers - center in local coordinate - relative to body is 0,0
joint_def.localAnchorA = new b2Vec2(-0.5, -0.5);
joint_def.localAnchorB = new b2Vec2(0.5, 0.5);

//difference in angle of each body
joint_def.referenceAngle = 0 * Math.PI / 3;

//add the joint to the world
world.CreateJoint(joint_def);

The joint definition needs to know the bodies to connect and the coordinates on each of them where the weld is to be done. It also has a referenceAngle parameter that defines the angle between the 2 bodies after being welded. Play with the referenceAngle to see the effect.
Source

/**
Weld Joint in box2d in javascript
Silver Moon (m00n.silv3r@gmail.com)
*/
var b2Vec2 = Box2D.Common.Math.b2Vec2
, b2AABB = Box2D.Collision.b2AABB
, b2BodyDef = Box2D.Dynamics.b2BodyDef
, b2Body = Box2D.Dynamics.b2Body
, b2FixtureDef = Box2D.Dynamics.b2FixtureDef
, b2Fixture = Box2D.Dynamics.b2Fixture
, b2World = Box2D.Dynamics.b2World
, b2PolygonShape = Box2D.Collision.Shapes.b2PolygonShape
, b2CircleShape = Box2D.Collision.Shapes.b2CircleShape
, b2DebugDraw = Box2D.Dynamics.b2DebugDraw
, b2MouseJointDef = Box2D.Dynamics.Joints.b2MouseJointDef
, b2WeldJointDef = Box2D.Dynamics.Joints.b2WeldJointDef
, b2Shape = Box2D.Collision.Shapes.b2Shape
;

var world;
var ctx;
var canvas_width;
var canvas_height;
var mouse_pressed = false;
var mouse_joint = false;
var mouse_x, mouse_y;

//box2d to...

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Weld joint in box2d in javascript