Emanuele Feronato

// the game itself
var game;

// the ball
var ballBody;

// the joint
var ballJoint;

// function to be executed when the window loads
window.onload = function() {	
     // starting the game itself
	game = new Phaser.Game(800, 600, Phaser.AUTO, "");
     // creation and execution of "PlayGame" state
     game.state.add("PlayGame",playGame);
     game.state.start("PlayGame");
}

var playGame = function(game){};

playGame.prototype = {
     // function to be executed onche game has been created
  	create: function(){
          // initializing Box2D physics
		game.physics.startSystem(Phaser.Physics.BOX2D);
          // making the debug draw show joints
          game.physics.box2d.debugDraw.joints = true;          
          // setting gravity
          game.physics.box2d.gravity.y = 500;
          // the ground
          var groundBody = new Phaser.Physics.Box2D.Body(game, null, 400, 595, 1);
          groundBody.setRectangle(800, 10, 0, 0);
          // adding some random bodies
          for(var i = 0; i < 10; i++){
               var randomBody =  new Phaser.Physics.Box2D.Body(game, null, game.rnd.between(100, 700), game.rnd.between(100, 400), 0);  
               randomBody.setRectangle(game.rnd.between(27, 75), game.rnd.between(25, 75), 0, 0);  
          }
          // the ball
          ballBody = new Phaser.Physics.Box2D.Body(game, null, 400, 550, 2);
          ballBody.setCircle(10);
          // waiting for player input then call addHook function
          game.input.onDown.add(addHook);
	},
     render: function(){
          // this is the debug draw in action
          game.debug.box2dWorld();
     },
     update: function(){
          // if there is a joint, make it shorter by 1%
          if(ballJoint){
               ballJoint.SetLength(ballJoint.GetLength() * 0.99);
          }
     }
}

function addHook(e){
     // this is how we get an array of bodies at a certain cordinate, in this case player input coordinate
	var currentBody = game.physics.box2d.getBodiesAtPoint(e.x, e.y);
	// if there is at least one body (but it can't be more than one in this example)...
	if(currentBody.length>0){	
		// if the body is not static (it's not the ground)
		if(currentBody[0].static){
               // waking up the body (it won't work on a sleeping body)
               ballBody.data.SetAwake(true);  
               // adding a distance joint
               ballJoint = game.physics.box2d.distanceJoint(ballBody, currentBody[0]);     
          }
          // update listeners
          game.input.onDown.remove(addHook);
          game.input.onUp.add(removeHook);
     }
}

function removeHook(){
     // update listeners
     game.input.onUp.remove(removeHook);
     game.input.onDown.add(addHook);
     // destroying the joint
     game.physics.box2d.world.DestroyJoint(ballJoint);
          
}