Class World

var world = new World(),
    body = new Body();
world.addBody(body);

var constraint = new LockConstraint(bodyA, bodyB);
world.addConstraint(constraint);

Use faster hash map to lookup from material id's

Should use an api similar to the raycast function

Should probably implement a .containsPoint method for all shapes. Would be more efficient

Should use the broadphase

Returning the hit shape would be fine - it carries a reference to the body now

var ray = new Ray({
    mode: Ray.ALL,
    from: [0, 0],
    to: [10, 0],
    callback: function(result){

        // Print some info about the hit
        console.log('Hit body and shape: ', result.body, result.shape);

        // Get the hit point
        var hitPoint = vec2.create();
        result.getHitPoint(hitPoint, ray);
        console.log('Hit point: ', hitPoint[0], hitPoint[1], ' at distance ' + result.getHitDistance(ray));

        // If you are happy with the hits you got this far, you can stop the traversal here:
        result.stop();
    }
});
var result = new RaycastResult();
world.raycast(result, ray);

var removeBody;
world.on("beginContact",function(event){
    // We cannot remove the body here since the world is still stepping.
    // Instead, schedule the body to be removed after the step is done.
    removeBody = body;
});
world.on("postStep",function(event){
    if(removeBody){
        // Safely remove the body from the world.
        world.removeBody(removeBody);
        removeBody = null;
    }
});

// Simple fixed timestepping without interpolation
var fixedTimeStep = 1 / 60;
var world = new World();
var body = new Body({ mass: 1 });
world.addBody(body);

function animate(){
    requestAnimationFrame(animate);
    world.step(fixedTimeStep);
    renderBody(body.position, body.angle);
}

// Start animation loop
requestAnimationFrame(animate);

// Fixed timestepping with interpolation
var maxSubSteps = 10;
var lastTimeSeconds;

function animate(time){
    requestAnimationFrame(animate);
    var timeSeconds = time / 1000;

    if(lastTimeSeconds){
        var deltaTime = timeSeconds - lastTimeSeconds;
        world.step(fixedTimeStep, deltaTime, maxSubSteps);
    }

    lastTimeSeconds = timeSeconds;

    renderBody(body.interpolatedPosition, body.interpolatedAngle);
}

// Start animation loop
requestAnimationFrame(animate);

http://bulletphysics.org/mediawiki-1.5.8/index.php/Stepping_The_World