how do i stop my character from jumping in midair?

i just want to make it jump once from the ground.
The jump code has *** on it to make it clear.
Here Is Code=

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

public class PlayerController : MonoBehaviour
{
    public float moveSpeed;
    public float jumpForce;
    public CharacterController controller;

    private Vector3 moveDirection;
    public float gravityScale;

    // Start is called bsefore the first frame update
    void Start()
    {
     controller = GetComponent<CharacterController>();
    }

    // Update is called once per frame
    void Update()
    {
     moveDirection = new Vector3(Input.GetAxis("Horizontal") * moveSpeed, 0f, Input.GetAxis("Vertical") * moveSpeed);

        ***if (controller.isGrounded)
        {
            if (Input.GetButtonDown("Jump"))
            {
                moveDirection.y = jumpForce;
            }
        }***

        moveDirection.y = moveDirection.y + (Physics.gravity.y * gravityScale);
        controller.Move(moveDirection * Time.deltaTime);

    }
}

I hope someone can answer this a soon as possible.

,

A very simple way to do this would be to have your “Is grounded” statement be true once the character hits the ground again, and any time you hit jump it will change it to false. Using the OnCollisionEnter function in Unity is a simple way to do it, for example,

void OnCollisionEnter(Collision col) {
		if (col.gameObject.tag == "Floor") {
			isGrounded = true;
		}
	}

And you would simply change your jump code to,

if (Input.GetButtonDown("Jump"))
        {
             moveDirection.y = jumpForce;
             isGrounded = false;
        }