Changing data-scroll-speeds with jQuery?

Question

I am using the code below to change the scroll speed of certain elements. Code I have copied from HERE.

To double check my overall code I have also added a color change to ".slogan-a-line".

The if/else is depending on if "#image-ul" is fully above the bottom edge of the browser window.

My problem is that –when either resizing or scrolling the browser window– the color of ".slogan-a-line" does change as it should, but the data-scroll-speeds on other elements do not. When (re)loading they do.

Initially, when first loading the webpage, the correct data-scroll-speed is set by the code. But when resizing the browser window –to change whether "#image-ul" is fully above the bottom edge of the browser window or not– the data scroll speeds do not change, till I refresh the webpage (so the id and class names are correct).

I need the data-scroll-speeds to change without having to refresh the browser window. Can anyone see what I have done wrong?

<script>
  // Assign attribute specific "data-scroll-speed" to elements upon loading, resizing and scrolling of the webpage page. "if/else" is depending on if #image-ul is fully above the bottom edge of the browser window.
  $(document).ready(function() {
    $(window).on('load resize scroll', function() {
      var WindowScrollTop = $(this).scrollTop(),
        Div_one_top = $('#image-ul').offset().top,
        Div_one_height = $('#image-ul').outerHeight(true),
        Window_height = $(this).outerHeight(true);
      if (WindowScrollTop + Window_height >= (Div_one_top + Div_one_height)) {
        $('#sloganenglish').attr('data-scroll-speed', '2');
        $('.slow-scroll-slider').attr('data-scroll-speed', '5');
        $('.slogan-a-line').css('color', 'green');
      } else {
        $('#sloganenglish').attr('data-scroll-speed', '1');
        $('.slow-scroll-slider').attr('data-scroll-speed', '1');
        $('.slogan-a-line').css('color', 'red');
      }
    }).scroll();
  });


  // data-scroll-speed script
  $.fn.moveIt = function() {
    var $window = $(window);
    var instances = [];

    $(this).each(function() {
      instances.push(new moveItItem($(this)));
    });

    window.onscroll = function() {
      var scrollTop = $window.scrollTop();
      instances.forEach(function(inst) {
        inst.update(scrollTop);
      });
    }
  }

  var moveItItem = function(el) {
    this.el = $(el);
    this.speed = parseInt(this.el.attr('data-scroll-speed'));
  };

  moveItItem.prototype.update = function(scrollTop) {
    var pos = scrollTop / this.speed;
    this.el.css('transform', 'translateY(' + -pos + 'px)');
  };

  // Initialization
  $(function() {
    $('[data-scroll-speed]').moveIt();
  });
</script>

score 0 · Answer 1 · answered Jun 07 '17 at 08:10

See an answer EXAMPLE HERE!

    //
// default speed ist the lowest valid scroll speed.
//
var default_speed = 1;
//
// speed increments defines the increase/decrease of the acceleration
// between current scroll speed and data-scroll-speed
//
var speed_increment = 0.01;
//
// maximum scroll speed of the elements
//
var data_scroll_speed_a = 4; // #sloganenglish
var data_scroll_speed_b = 5; // .slogan-a-line
//
//
//
var increase_speed, decrease_speed, target_speed, current_speed, speed_increments;
$(document).ready(function() {
     $(window).on('load resize scroll', function() {
         var WindowScrollTop = $(this).scrollTop(),
             Div_one_top = $('#image-ul').offset().top,
             Div_one_height = $('#image-ul').outerHeight(true),
             Window_height = $(this).outerHeight(true);
         if (WindowScrollTop + Window_height >= (Div_one_top + Div_one_height)) {
             $('#sloganenglish').attr('data-scroll-speed', data_scroll_speed_a).attr('data-current-scroll-speed', default_speed).attr('data-speed-increments', data_scroll_speed_a * speed_increment);
             $('.slogan-a-line').attr('data-scroll-speed', data_scroll_speed_b).attr('data-current-scroll-speed', default_speed).attr('data-speed-increments', data_scroll_speed_b * speed_increment);
             $('.slogan-a-line').css('color', 'yellow');
             increase_speed = true;
             decrease_speed = false;
         } else {
             $('#sloganenglish').attr('data-scroll-speed', '1').attr('data-current-scroll-speed', default_speed);
             $('.slogan-a-line').attr('data-scroll-speed', '1').attr('data-current-scroll-speed', default_speed);
             $('.slogan-a-line').css('color', 'red');
             decrease_speed = true;
             increase_speed = false;
         }
     }).scroll();
 });


 // data-scroll-speed script
 $.fn.moveIt = function() {
     var $window = $(window);
     var instances = [];

     $(this).each(function() {
         instances.push(new moveItItem($(this)));
     });

     window.onscroll = function() {
         var scrollTop = $window.scrollTop();
         instances.forEach(function(inst) {
             inst.update(scrollTop);
         });
     }
 }

 var moveItItem = function(el) {
     this.el = $(el);
     this.speed = parseInt(this.el.attr('data-scroll-speed'));
     this.current_speed = 1.0;
 };

 moveItItem.prototype.update = function(scrollTop) {

     target_speed = parseInt(this.el.attr('data-scroll-speed'));
     current_speed = this.current_speed;
     speed_increments = parseFloat(this.el.attr('data-speed-increments'));

     if(increase_speed){
         if(current_speed < target_speed){
              current_speed += speed_increments;
         } else {
            current_speed = target_speed;
         }
     } else if(decrease_speed){
         if(current_speed > default_speed){
            current_speed -= speed_increments;
         }
         if($(window).scrollTop() === 0){
            current_speed = default_speed;
         }
     }
     this.current_speed = current_speed;
     var pos = scrollTop / this.current_speed;
     this.el.css('transform', 'translateY(' + -pos + 'px)');
 };

 // Initialization
 $(function() {
     $('[data-scroll-speed]').moveIt();
 });

Changing data-scroll-speeds with jQuery?

1 Answers1