Move GameObject back and forth

I got an Object that I want to move up to Point A and when it reaches Point A it should move to Point B. When it reaches Point B it should move back to Point A.

I thought I could use Vector3.Lerp for this

void Update()
{
  transform.position = Vector3.Lerp(pointA, pointB, speed * Time.deltaTime);
}

But how can i move back then? Is there an elegant way to archieve this? Obviously I would need 2 Lerps like this way:

void Update()
{
  transform.position = Vector3.Lerp(pointA, pointB, speed * Time.deltaTime); // Move up
  transform.position = Vector3.Lerp(pointB, pointA, speed * Time.deltaTime); // Move down
}

Could someone help me out?

Solution 1:

There are many ways to do this but Mathf.PingPong is the easiest and the simplest way to accomplish this. Use Mathf.PingPong to get number between 0 and 1 then pass that value to Vector3.Lerp. That's it.

Mathf.PingPong will automatically return value will that will move back and forth between 0 and 1. Read the linked documentation for more info.

public float speed = 1.19f;
Vector3 pointA;
Vector3 pointB;

void Start()
{
    pointA = new Vector3(0, 0, 0);
    pointB = new Vector3(5, 0, 0);
}

void Update()
{
    //PingPong between 0 and 1
    float time = Mathf.PingPong(Time.time * speed, 1);
    transform.position = Vector3.Lerp(pointA, pointB, time);
}