jumping error!?

It's unknown because you haven't defined it anywhere. You need to define variables before you can use them.

Try this.

var jumpSpeed = 5.0; var moveDirection : Vector3;

I believe you should be approaching this issue in a different way, I recommend you to use AddForce and study a little about the Rigidbody2d component in your Player, also check about ForceMode like Impulse. https://docs.unity3d.com/ScriptReference/Rigidbody2D.AddForce.html https://docs.unity3d.com/ScriptReference/ForceMode2D.html

  public float Speed;
  void FixedUpdate()
  {
 
      if (Input.GetKey(KeyCode.Space))
      {
 
          GetComponent<Rigidbody2D>().AddForce(Vector2.up* Speed);
      }
  }

var jumpSpeed = 5.0; var moveDirection Vector2; if(Input.GetKeyDown("UpArrow"))

{

moveDirection.y = jumpSpeed;

} //this is javascript, so not good at javascript // lower 1 is c# //============ public float jumpSpeed; public Rigidbody2D rb2d; void Start() { rb2d = GetComponent(); }

void Update() {

   if (Input.GetKey("up"))
   {
      Vector2 movement = new Vector2(0, 5);
       if(movement != Vector2.zero) {
       rb2d.AddForce(movement * jumpSpeed);

} } }