scrollToElement function using javascript

this javascript content:

function scrollToElement(elementSelector, instance = 0) {
  const elements = document.querySelectorAll(elementSelector);
  if (elements.length > instance) {
   elements[instance].scrollIntoView({ behavior: "smooth" });
  }
 }

const link1 = document.getElementById("link1");
const link2 = document.getElementById("link2");
const link3 = document.getElementById("link3");

link1.addEventListener("click", () => {
  scrollToElement(".header");
});

but i not understand this and why it used instance and what tthe relation between elements.length and instance

>Solution :

so here,scrollToElement() function takes two arguments:

elementSelector: A CSS selector that matches the element to scroll to.
instance: The index of the element to scroll to. Defaults to 0.

The function first gets all the elements that match the CSS selector using the document.querySelectorAll() method.

Then, it checks if the number of elements is greater than the instance argument.

If it is, the function scrolls the instance element into view using the element.scrollIntoView() method.

The scrollIntoView() method takes an optional parameter called behavior which specifies how the scrolling should be animated.

In this case, you are setting it to smooth so that the scrolling is animated smoothly.

The scrollToElement() function is called when the user clicks on the link1 element.

The elementSelector argument is set to .header, which matches the CSS selector for the header element.

The instance argument is set to 0, which means that the function will scroll to the first header element that it finds.

In summary, the code will scroll to the first header element on the page when the user clicks on the link1 element.