How do I make a character jump only once in Unity 2D?,How do I make a character Jump only once?

When I press the "Space" or "W" Key assigned to jump, I am able to continously jump in midair. How am I able to limit this to a double jump in the Rigidbody2D?

using System.Collections; using System.Collections.Generic; using UnityEngine;

public class PlayerMovement : MonoBehaviour { private Rigidbody2D rb2d; public float speed; private bool Constraint; private Animator animCharacter; public Vector2 JumpVelocity; public float jump; float moveVelocity; bool grounded = false;

 void Start()
 {
     rb2d = GetComponent<Rigidbody2D>();
     animCharacter = GetComponent<Animator>();
 }
  void FixedUpdate()
 {

     if (Input.GetKeyDown(KeyCode.Space) || Input.GetKeyDown (KeyCode.W))
     {
         rb2d.velocity = new Vector2(rb2d.velocity.x, jump);
         animCharacter.SetTrigger("Jump Activated");
         
     }

     rb2d = GetComponent<Rigidbody2D>();
     if (rb2d.velocity.y == 0)
     {
         animCharacter.SetTrigger("Grounded");

     }

     if (Input.GetKey(KeyCode.D)) rb2d.velocity += Vector2.right * speed;

     if (Input.GetKey(KeyCode.A))
     {
         rb2d.velocity = new Vector2(-speed, rb2d.velocity.y);
     }
     else if (Input.GetKey(KeyCode.D))
     {
         rb2d.velocity = new Vector2(speed, rb2d.velocity.y);
     }

     else
         rb2d.velocity = new Vector2(0, rb2d.velocity.y);
 }

} ,When I press the "Space" or "W" keys assigned to Jump, I am able to continously jump in midair. How am I able to fix this?

using System.Collections; using System.Collections.Generic; using UnityEngine;

public class PlayerMovement : MonoBehaviour { private Rigidbody2D rb2d; public float speed; private bool Constraint; private Animator animCharacter; public Vector2 JumpVelocity; public float jump; float moveVelocity; bool grounded = false;

 void Start()
 {
     rb2d = GetComponent<Rigidbody2D>();
     animCharacter = GetComponent<Animator>();
 }
  void FixedUpdate()
 {

     if (Input.GetKeyDown(KeyCode.Space) || Input.GetKeyDown (KeyCode.W))
     {
         rb2d.velocity = new Vector2(rb2d.velocity.x, jump);
         animCharacter.SetTrigger("Jump Activated");
         
     }

     rb2d = GetComponent<Rigidbody2D>();
     if (rb2d.velocity.y == 0)
     {
         animCharacter.SetTrigger("Grounded");

     }

     if (Input.GetKey(KeyCode.D)) rb2d.velocity += Vector2.right * speed;

     if (Input.GetKey(KeyCode.A))
     {
         rb2d.velocity = new Vector2(-speed, rb2d.velocity.y);
     }
     else if (Input.GetKey(KeyCode.D))
     {
         rb2d.velocity = new Vector2(speed, rb2d.velocity.y);
     }

     else
         rb2d.velocity = new Vector2(0, rb2d.velocity.y);
 }

}