Scroll event listener javascript

Question

Is there a js listener for when a user scrolls in a certain textbox that can be used? Kinda like onclick except for scrolling. I saw HTML5 event listener for number input scroll - Chrome only but that seems to be for chrome only. I'm looking for something cross-browser.

Answer 1

For those who found this question hoping to find an answer that doesn't involve jQuery, you hook into the window "scroll" event using normal event listening. Say we want to add scroll listening to a number of CSS-selector-able elements:

// what should we do when scrolling occurs
function runOnScroll(element) {
  // not the most exciting thing, but a thing nonetheless
  console.log(element);
};

// grab elements as array, rather than as NodeList
const elements = document.querySelectorAll(`...`);

// and then make each element do something on scroll
elements.forEach(element => {
  window.addEventListener(
    "scroll",
    () => runOnScroll(element),
    { passive: true }
  );
});

Or alternatively, bind a single scroll listener, with evt => runOnScroll(evt) as handler and then figure out what to do with everything in elements inside the runOnScroll function instead.

Note that we're using the passive attribute to tell the browser that this event won't interfere with scrolling itself. This is important if we want smooth scrolling behaviour (and also means we shouldn't do perform reflow-triggering DOM updates during scroll).

For bonus points, you can give the scroll handler a lock mechanism so that it doesn't run if we're already scrolling:

// global lock, so put this code in a closure of some sort so you're not polluting.
let locked = false;
let lastCall = false;

function runOnScroll(element) {
  if(locked) return;

  if (lastCall) clearTimeout(lastCall);
  lastCall = setTimeout(() => {
    runOnScroll(element);
    // you do this because you want to handle the last
    // scroll event, even if it occurred while another
    // event was being processed.
  }, 200);

  // ...your code goes here...

  locked = false;
};