FPS animation problem!

Before I start I just want to say that I am a complete noob when it comes to scripting, I literally started a week ago.... With the script below and slight tweaking of the options I have managed to get the animations to do the following: Show walk animation when holding W key quikly change to an idle animation when pressing nothing and an on the spot jump animation.

this is what I want to happen: When walking forwards I want to be able to jump, have the animation for jumping play, then while still holding the w key when the jump animation has stoped to change back to the walk animation.

the problem is that if I'm walking and jump, the jump animation plays but when I land all animations stop...

basically I want the animations to be smooth with each other.

this is the code Im using (javascript) is there anyway to fix this?

     function Update(){
     if(Input.GetKey("up")){
     animation.CrossFade("walkanim2");
     }
     if(Input.GetKey("w")){
     animation.CrossFade("walkanim2");
     }
     if(Input.GetKeyDown("space"))
     {
     animation.CrossFade("jump");
     }
     if(Input.GetKeyUp("up")){
     animation.CrossFade("animstop");
     }
     if(Input.GetKeyUp("w"))
     {
     animation.CrossFade("animstop");
     }
 }