debounce.js

//Debounce returns a function, based on input:
//1. trigger function for debouncing - func
//2. time to debounce (waiting time - only call after this amount of secs passed - wait
//3. immediate - true/false whether trigger function immediately or wait until the debouncing time.
//Logic:
//1. Save arguments, save context
//2. Clear timeout - start again the counter
//3. if (immediate and no timeout - aka first run - run it.
//4. set Time out for triggering func with wait time, in which if not immediate (false), then clear timeout and trigger func.
function debounce(func, wait, immediate = false){
  var timeout;
  
  return function(){
    var context = this, args = arguments;
    var later = function(){
      timeout = null;
      if(!immediate){
        func.apply(context, args);
      };
      var callNow = immediate && !timeout;
      clearTimeout(timeout);
     
      timeout = setTimeout(later, wait);
      if (callNow){
        func.apply(context, args);
      }
    }
  }
}

Test.js

function handleScroll(){

}

var handleScrollListener = debounce(handleScroll, 200);

window.addEventListener('scroll', handleScrollListener);