Jumping on moving platforms problem c#

I’m trying to create a code that would let me jump while standing on moving platforms, but I can’t think of a way to do it. I wrote a function that checks to see if I’m on a platform and returns true (or false if I’m not), but I want this to be checked whenever I try to jump (with the space bar), such that I can only jump while onPlatform is true.

Basically, how can I program a function that returns booleans to work everytime I press a button? Is that even what I should try to do? Here’s my code.

using UnityEngine;
using System.Collections;

public class LRmovement : MonoBehaviour {
public float speed = 1f;
public float JumpSpeed = 10f;
private bool onPlatform;

void Start () {

}

void Update () {
	if (Input.GetKey (KeyCode.D) && (transform.position.x < 1.5))
			transform.position += new Vector3 (speed * Time.deltaTime, 0.0f, 0.0f);

	if (Input.GetKey (KeyCode.A) && (transform.position.x > -1.5))
			transform.position -= new Vector3 (speed * Time.deltaTime, 0.0f, 0.0f);

}

}

Hi,

If IsOnPlateform() is your function that returns a boolean

bool IsOnPlateform () {
   //something with probably a raycast downward
}

You just need to call it in an if condition like you do to check if you can move on the right or on the left:

void Update () {
   //your stuff

   if (Input.GetKeyDown(Keycode.Space) && IsOnPlateform())
      Jump();
}

private void Jump () {
   //set vertical velocity of your character to 0
   //add a vertical force upward so it jumps
}