Typescript active element focus

Question

I have a section with a class name 'concert-landing-synopsis' and on a scroll, I want to check if the section is on focus and add a class name to a different element. I have looked through some of the solutions here the focused variable is always false

let activateElement = document.getElementsByClassName("concert-landing-synopsis");

if (activateElement.length > 0) {
  window.onscroll = _ => {
    let isFocused = (document.activeElement === activateElement[0]);

    if (isFocused) {
      console.log("On focus");
    }
  };
}

The view is something like this

<section class="concert-landing-details">
  <div></div>
  <div></div>
  <div></div>
  <div></div>
</section>

The section element isn't focusable. You can see here https://stackoverflow.com/questions/1599660/which-html-elements-can-receive-focus what elements are actually focusable. — shyyko.serhiy, Dec 19 '18 at 22:07
What I imagine you are trying to achieve is to check if the element is visible in scrollable container. You should see https://stackoverflow.com/questions/487073/how-to-check-if-element-is-visible-after-scrolling . — shyyko.serhiy, Dec 19 '18 at 22:09

Harrison Cole · Answer 1 · 2018-12-19T23:12:13.813

0

You need to loop through all the elements returned by document.getElementsByClassName('concert-landing-synopsis'), as in

document.getElementsByClassName('concert-landing-synopsis').forEach((el) => {
   const isFocused = (document.activeElement === el);
});

edited Dec 19 '18 at 23:12

answered Dec 19 '18 at 22:21

Harrison Cole

31
6

Typescript active element focus

1 Answers1