This code can check view is in block or not - IntersectionObserver

inview-check-javascript-IntersectionObserver

var get_started_block = document.getElementById("get-started");
var float_button = document.getElementById("float-btn");

function handler(entries, observer) {
  for (entry of entries) {
    if (entry.isIntersecting) {
        float_button.style.display = "none";
    }else{
        float_button.style.display = "block";
    }
  }
}

/* By default, invokes the handler whenever:
   1. Any part of the target enters the viewport
   2. The last part of the target leaves the viewport */

let observer = new IntersectionObserver(handler);
observer.observe(get_started_block);