code: function( data ){
  
              var self = this
                  ,state
                  ,dt = Math.max(data.dt, self.options.moveThrottle)
                  ,body
                  ,d
                  ;
  
              // if we have one or more bodies grabbed, we need to move them to the new mouse/finger positions.
              // we'll do this by adjusting the velocity so they get there at the next step
              for ( var touchId in self.bodyData ) {
                  d = self.bodyData[touchId];
                  body = d.body;
                  state = body.state;
                  state.vel.clone( d.pos ).vsub( d.offset ).vsub( state.pos ).mult( 1 / dt );
              }
          }
docs: extended