how to change the sprite in sprite renderer through script in unity code example

Example 1: change sprite of gameobject unity

gameObjectName.GetComponent<SpriteRenderer>().sprite = spriteName;

Example 2: change sprite of a sprite unity

public SpriteRenderer spriteRenderer;
public Sprite newSprite;

void ChangeSprite()
    {
        spriteRenderer.sprite = newSprite; 
    }