Input.GetKeyDown is won't work properly Unity 2D - unity3d

Question

I'm trying to make my square jump in Unity 2D when I press Space button. I have the following code:
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
public class Movement : MonoBehaviour
{
public float moveSpeed;
public float jumpSpeed;
float moveX;
Vector2 pos;
// Update is called once per frame
void Update()
{
MoveHorizontally();
Jump();
}
void MoveHorizontally(){
moveX = Input.GetAxis("Horizontal") * Time.deltaTime;
pos.x = moveX * moveSpeed;
transform.position = new Vector2(transform.position.x + pos.x,transform.position.y + pos.y);
}
void Jump(){
if (Input.GetKeyDown("space")){
GetComponent<Rigidbody2D>().AddForce(new Vector2(0,jumpSpeed * Time.deltaTime), ForceMode2D.Impulse);
Debug.Log("Jumped!");
}
}
}
When I press Space button, "Jumped!" message shows up, but my square not jumping. Any idea?
Thanks a lot.
I tried using Input.GetKey function. It works, but that function keeps making my square go upwards if i keep holding Space button.

Answer 1

U need to assing a value to jumpforce. and of course to the moveforce. if u dont wanna jump repeatly Just name a bool for checking if u are on ground. I use mine as" private bool = isGrounded".
and try the code below. It makes ur jump a condition as a function of touching ground.
private void OnCollisionEnter2D(Collision2D collision)
{
if (collision.gameObject.CompareTag("Ground"))
isGrounded = true;
}
and here is my code for jump.
public void PlayerJump() {
if (Input.GetButtonDown("Jump") && isGrounded) {
isGrounded = false;
myBody.AddForce(new Vector2(0f, jumpForce), ForceMode2D.Impulse);
}
}
whenever u jump it makes your bool variant false and whenever u touch ground it make ur bool true.
Make sure "Ground" must be same exactly the tag your ground has.

Answer 2

When you call AddForce() method you don't have to multiply with "Time.deltaTime".
What you can do is the following:
First cached your "Rigidbody2D" component from your Start() method because if you call it every frame it will affect your game performance.
private Rigidbody2D rigidbody2D;
void Start()
{
rigidbody2D = GetComponent<Rigidbody2D>();
}
Second, instead of Update() method you should call the FixedUpdate() method which is recommended when you deal with Physics
void FixedUpdate()
{
MoveHorizontally();
Jump();
}
Third, on your Jump() method as I said on top you should not multiply the jump force with Time.deltaTime, instead do the following:
public float jumpForce = 10f;
public void Jump()
{
if (Input.GetKeyDown(KeyCode.Space))
{
rigidbody2D.AddForce(Vector2.up*jumpForce);
}
}
You can adjust the jumpForce as you want.
Also Vector2.up is a shorthand for writing Vector2(0, 1)
You can read more about Vector2 here Vector2.up Unity's Documentation