third person double jump

please guys can someone edit me this so i can "double jump" , help please im stuck :( btw im using the default "third person controller" script

 // Require a character controller to be attached to the same game object
 @script RequireComponent(CharacterController)
 
 public var idleAnimation : AnimationClip;
 public var walkAnimation : AnimationClip;
 public var jumpPoseAnimation : AnimationClip;
 
 public var walkMaxAnimationSpeed : float = 0.75;
 public var trotMaxAnimationSpeed : float = 1.0;
 public var jumpAnimationSpeed : float = 1.15;
 public var landAnimationSpeed : float = 1.0;
 
 private var _animation : Animation;
 
 enum CharacterState {
     Idle = 0,
     Walking = 1,
     Trotting = 2,
     Jumping = 4,
 }
 
 private var _characterState : CharacterState;
 
 // The speed when walking
 var walkSpeed = 2.0;
 
 
 
 
 // after trotAfterSeconds of walking we trot with trotSpeed
 var trotSpeed = 4.0;
 
 var inAirControlAcceleration = 3.0;
 
 
 // How high do we jump when pressing jump and letting go immediately
 var jumpHeight = 0.5;
 
 // The gravity for the character
 var gravity = 20.0;
 // The gravity in controlled descent mode
 var speedSmoothing = 10.0;
 var rotateSpeed = 500.0;
 var trotAfterSeconds = 3.0;
 
 var canJump = true;
 
 
 private var jumpRepeatTime = 0.05;
 private var jumpTimeout = 0.15;
 private var groundedTimeout = 0.25;
 
 // The camera doesnt start following the target immediately but waits for a split second to avoid too much waving around.
 private var lockCameraTimer = 0.0;
 
 // The current move direction in x-z
 private var moveDirection = Vector3.zero;
 // The current vertical speed
 private var verticalSpeed = 0.0;
 // The current x-z move speed
 private var moveSpeed = 0.0;
 
 // The last collision flags returned from controller.Move
 private var collisionFlags : CollisionFlags; 
 
 // Are we jumping? (Initiated with jump button and not grounded yet)
 private var jumping = false;
 private var jumpingReachedApex = false;
 
 // Are we moving backwards (This locks the camera to not do a 180 degree spin)
 private var movingBack = false;
 // Is the user pressing any keys?
 private var isMoving = false;
 // When did the user start walking (Used for going into trot after a while)
 private var walkTimeStart = 0.0;
 // Last time the jump button was clicked down
 private var lastJumpButtonTime = -10.0;
 // Last time we performed a jump
 private var lastJumpTime = -1.0;
 
 
 
 // the height we jumped from (Used to determine for how long to apply extra jump power after jumping.)
 private var lastJumpStartHeight = 0.0;
 
 
 private var inAirVelocity = Vector3.zero;
 
 private var lastGroundedTime = 0.0;
 
 
 private var isControllable = true;
 
 
 function Awake ()
 {
     moveDirection = transform.TransformDirection(Vector3.forward);
     
     _animation = GetComponent(Animation);
     if(!_animation)
         Debug.Log("The character you would like to control doesn't have animations. Moving her might look weird.");
     
     /*
 public var idleAnimation : AnimationClip;
 public var walkAnimation : AnimationClip;
 public var jumpPoseAnimation : AnimationClip;    
     */
     if(!idleAnimation) {
         _animation = null;
         Debug.Log("No idle animation found. Turning off animations.");
     }
     if(!walkAnimation) {
         _animation = null;
         Debug.Log("No walk animation found. Turning off animations.");
     }
     
     if(!jumpPoseAnimation && canJump) {
         _animation = null;
         Debug.Log("No jump animation found and the character has canJump enabled. Turning off animations.");
     }
             
 }
 
 
 function UpdateSmoothedMovementDirection ()
 {
     var cameraTransform = Camera.main.transform;
     var grounded = IsGrounded();
     
     // Forward vector relative to the camera along the x-z plane    
     var forward = cameraTransform.TransformDirection(Vector3.forward);
     forward.y = 0;
     forward = forward.normalized;
 
     // Right vector relative to the camera
     // Always orthogonal to the forward vector
     var right = Vector3(forward.z, 0, -forward.x);
 
     var v = Input.GetAxisRaw("Vertical");
     var h = Input.GetAxisRaw("Horizontal");
 
     // Are we moving backwards or looking backwards
     if (v < -0.2)
         movingBack = true;
     else
         movingBack = false;
     
     var wasMoving = isMoving;
     isMoving = Mathf.Abs (h) > 0.1 || Mathf.Abs (v) > 0.1;
         
     // Target direction relative to the camera
     var targetDirection = h * right + v * forward;
     
     // Grounded controls
     if (grounded)
     {
         // Lock camera for short period when transitioning moving & standing still
         lockCameraTimer += Time.deltaTime;
         if (isMoving != wasMoving)
             lockCameraTimer = 0.0;
 
         // We store speed and direction seperately,
         // so that when the character stands still we still have a valid forward direction
         // moveDirection is always normalized, and we only update it if there is user input.
         if (targetDirection != Vector3.zero)
         {
             // If we are really slow, just snap to the target direction
             if (moveSpeed < walkSpeed * 0.9 && grounded)
             {
                 moveDirection = targetDirection.normalized;
             }
             // Otherwise smoothly turn towards it
             else
             {
                 moveDirection = Vector3.RotateTowards(moveDirection, targetDirection, rotateSpeed * Mathf.Deg2Rad * Time.deltaTime, 1000);
                 
                 moveDirection = moveDirection.normalized;
             }
         }
         
         
         
         // Smooth the speed based on the current target direction
         var curSmooth = speedSmoothing * Time.deltaTime;
         
         // Choose target speed
         //* We want to support analog input but make sure you cant walk faster diagonally than just forward or sideways
         var targetSpeed = Mathf.Min(targetDirection.magnitude, 1.0);
     
         _characterState = CharacterState.Idle;
         
         // Pick speed modifier
         if (Input.GetKey (KeyCode.Insert))
         {
             
         }
         else if (Time.time - trotAfterSeconds > walkTimeStart)
         {
             targetSpeed *= trotSpeed;
             _characterState = CharacterState.Trotting;
         }
         else
         {
             targetSpeed *= walkSpeed;
             _characterState = CharacterState.Walking;
         }
         
         moveSpeed = Mathf.Lerp(moveSpeed, targetSpeed, curSmooth);
         
         // Reset walk time start when we slow down
         if (moveSpeed < walkSpeed * 0.3)
             walkTimeStart = Time.time;
     }
     // In air controls
     else
     {
         // Lock camera while in air
         if (jumping)
             lockCameraTimer = 0.0;
             if (targetDirection != Vector3.zero)
         {
             // If we are really slow, just snap to the target direction
             if (moveSpeed < walkSpeed * 0.9 && grounded)
             {
                 moveDirection = targetDirection.normalized;
             }
             // Otherwise smoothly turn towards it
             else
             {
                 moveDirection = Vector3.RotateTowards(moveDirection, targetDirection, rotateSpeed * Mathf.Deg2Rad * Time.deltaTime, 1000);
                 
                 moveDirection = moveDirection.normalized;
             }
         }
 
         if (isMoving)
             inAirVelocity += targetDirection.normalized * Time.deltaTime * inAirControlAcceleration;
     }
     
 
         
 }
 
 
 function ApplyJumping ()
 {
     // Prevent jumping too fast after each other
     if (lastJumpTime + jumpRepeatTime > Time.time)
         return;
 
     if (IsGrounded()) {
         // Jump
         // - Only when pressing the button down
         // - With a timeout so you can press the button slightly before landing        
         if (canJump && Time.time < lastJumpButtonTime + jumpTimeout) {
             verticalSpeed = CalculateJumpVerticalSpeed (jumpHeight);
             SendMessage("DidJump", SendMessageOptions.DontRequireReceiver);
         }
     }
 }
 
 
 function ApplyGravity ()
 {
     if (isControllable)    // don't move player at all if not controllable.
     {
         // Apply gravity
         var jumpButton = Input.GetButton("Jump");
         
         // When we reach the apex of the jump we send out a message
         if (jumping && !jumpingReachedApex && verticalSpeed <= 0.0)
         {
             jumpingReachedApex = true;
             SendMessage("DidJumpReachApex", SendMessageOptions.DontRequireReceiver);
         }
     
         if (IsGrounded ())
             verticalSpeed = 0.0;
         else
             verticalSpeed -= gravity * Time.deltaTime;
     }
 }
 
 function CalculateJumpVerticalSpeed (targetJumpHeight : float)
 {
     // From the jump height and gravity we deduce the upwards speed 
     // for the character to reach at the apex.
     return Mathf.Sqrt(2 * targetJumpHeight * gravity);
 }
 
 function DidJump ()
 {
     jumping = true;
     jumpingReachedApex = false;
     lastJumpTime = Time.time;
     lastJumpStartHeight = transform.position.y;
     lastJumpButtonTime = -10;
     
     _characterState = CharacterState.Jumping;
 }
 
 function Update() {
 
     
     if (!isControllable)
     {
         // kill all inputs if not controllable.
         Input.ResetInputAxes();
     }
 
     if (Input.GetButtonDown ("Jump"))
     {
         lastJumpButtonTime = Time.time;
     }
 
     UpdateSmoothedMovementDirection();
     
     // Apply gravity
     // - extra power jump modifies gravity
     // - controlledDescent mode modifies gravity
     ApplyGravity ();
 
     // Apply jumping logic
     ApplyJumping ();
     
     // Calculate actual motion
     var movement = moveDirection * moveSpeed + Vector3 (0, verticalSpeed, 0) + inAirVelocity;
     movement *= Time.deltaTime;
     
     // Move the controller
     var controller : CharacterController = GetComponent(CharacterController);
     collisionFlags = controller.Move(movement);
     
     // ANIMATION sector
     if(_animation) {
         if(_characterState == CharacterState.Jumping) 
         {
             if(!jumpingReachedApex) {
                 _animation[jumpPoseAnimation.name].speed = jumpAnimationSpeed;
                 _animation[jumpPoseAnimation.name].wrapMode = WrapMode.ClampForever;
                 _animation.CrossFade(jumpPoseAnimation.name);
             } else {
                 _animation[jumpPoseAnimation.name].speed = landAnimationSpeed;
                 _animation[jumpPoseAnimation.name].wrapMode = WrapMode.ClampForever;
                 _animation.CrossFade(jumpPoseAnimation.name);                
             }
         } 
         else 
         {
             if(controller.velocity.sqrMagnitude < 0.1) {
                 _animation.CrossFade(idleAnimation.name);
             }
             else 
             {
                 
                  if(_characterState == CharacterState.Trotting) {
                     _animation[walkAnimation.name].speed = Mathf.Clamp(controller.velocity.magnitude, 0.0, trotMaxAnimationSpeed);
                     _animation.CrossFade(walkAnimation.name);    
                 }
                 else if(_characterState == CharacterState.Walking) {
                     _animation[walkAnimation.name].speed = Mathf.Clamp(controller.velocity.magnitude, 0.0, walkMaxAnimationSpeed);
                     _animation.CrossFade(walkAnimation.name);    
                 }
                 
             }
         }
     }
     // ANIMATION sector
     
     // Set rotation to the move direction
     if (IsGrounded())
     {
         
         transform.rotation = Quaternion.LookRotation(moveDirection);
             
     }    
     else
     {
         var xzMove = movement;
         xzMove.y = 0;
         if (xzMove.sqrMagnitude > 0.001)
         {
             transform.rotation = Quaternion.LookRotation(xzMove);
         }
     }    
     
     // We are in jump mode but just became grounded
     if (IsGrounded())
     {
     animation.wrapMode = WrapMode.Once;
           inAirVelocity = Vector3.zero;
         if (jumping)
         {
         animation.Play("jumpland"); // name of the animation clip 
         lastGroundedTime = Time.time;
             jumping = false;
             SendMessage("DidLand", SendMessageOptions.DontRequireReceiver);
         }
     }
 }
 function OnControllerColliderHit (hit : ControllerColliderHit )
 {
 //    Debug.DrawRay(hit.point, hit.normal);
     if (hit.moveDirection.y > 0.01) 
         return;
 }
 
 function GetSpeed () {
     return moveSpeed;
 }
 
 function IsJumping () {
     return jumping;
 }
 
 function IsGrounded () {
     return (collisionFlags & CollisionFlags.CollidedBelow) != 0;
 }
 
 function GetDirection () {
     return moveDirection;
 }
 
 function IsMovingBackwards () {
     return movingBack;
 }
 
 function GetLockCameraTimer () 
 {
     return lockCameraTimer;
 }
 
 function IsMoving ()  : boolean
 {
     return Mathf.Abs(Input.GetAxisRaw("Vertical")) + Mathf.Abs(Input.GetAxisRaw("Horizontal")) > 0.5;
 }
 
 function HasJumpReachedApex ()
 {
     return jumpingReachedApex;
 }
 
 function IsGroundedWithTimeout ()
 {
     return lastGroundedTime + groundedTimeout > Time.time;
 }
 
 function Reset ()
 {
     gameObject.tag = "Player";
 }