JavaScript Debounce Function

debounce.js

//source: https://remysharp.com/2010/07/21/throttling-function-calls 

/* Let us work on performance issues while making resource-intensive things */
  /* Will wait until event is not stopped and wait param is finished, then the callback will be fired */
  function _debounce(func, wait, immediate) {
    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);
    };
  };

// Usage:
  $(window).on('scroll', _debounce(function() {
    if ($(this).scrollTop() > $(this).height()) {
      $("#scroll-to-top").addClass('visible');
    } else {
      $("#scroll-to-top").removeClass('visible');
    }
  }, 500));