How to stop spam jumping?

I have a basic 2d movement script, but the only problem is you can spam the space bar and fly, is it possible to stop this?

 #pragma strict
 var movespeed : float =6.0f;
 var jumpspeed : float = 200f;
 var gravity : float = 1f;
 var jumpSpeed : float = 100f;
 
 
 
 
 function Start () {
     timer1 = 0;
 }
 
 function Update () {
       
         
 if(Input.GetKey(KeyCode.A)){
 transform.Translate(Vector3.left * movespeed * Time.deltaTime);
 }
 
 if(Input.GetKey(KeyCode.D)){
 transform.Translate(Vector3.right * movespeed * Time.deltaTime);
 }
 
 
     if (Input.GetKeyDown(KeyCode.Space)) {
          
         rigidbody.AddRelativeForce(0, jumpSpeed, 0);
         timer1 = 10;
           
         
         }
     }