Can I change the scroll speed using css or jQuery?

Solution 1:

The scroll speed CAN be changed, adjusted, reversed, all of the above - via javascript (or a js library such as jQuery).

WHY would you want to do this? Parallax is just one of the reasons. I have no idea why anyone would argue against doing so -- the same negative arguments can be made against hiding DIVs, sliding elements up/down, etc. Websites are always a combination of technical functionality and UX design -- a good designer can use almost any technical capability to improve UX. That is what makes him/her good.

Toni Almeida of Portugal created a brilliant demo, reproduced below:

jsFiddle Demo

HTML:

<div id="myDiv">
    Use the mouse wheel (not the scroll bar) to scroll this DIV. You will see that the scroll eventually slows down, and then stops. <span class="boldit">Use the mouse wheel (not the scroll bar) to scroll this DIV. You will see that the scroll eventually slows down, and then stops. </span>
</div>

javascript/jQuery:

  function wheel(event) {
      var delta = 0;
      if (event.wheelDelta) {(delta = event.wheelDelta / 120);}
      else if (event.detail) {(delta = -event.detail / 3);}

      handle(delta);
      if (event.preventDefault) {(event.preventDefault());}
      event.returnValue = false;
  }

  function handle(delta) {
      var time = 1000;
      var distance = 300;

      $('html, body').stop().animate({
          scrollTop: $(window).scrollTop() - (distance * delta)
      }, time );
  }

  if (window.addEventListener) {window.addEventListener('DOMMouseScroll', wheel, false);}
    window.onmousewheel = document.onmousewheel = wheel;

Source:

How to change default scrollspeed,scrollamount,scrollinertia of a webpage

Solution 2:

The mouse scroll even can be overwritten using JS within the browser using an event listener. It is possible to prevent default scrolling behavior this way, and implement your own behavior (see cssyphus's answer).

However, I think doing so is a HORRIBLE idea in terms of usability, accessibility, and respect for your users.

Solution 3:

I just made a pure Javascript function based on that code. Javascript only version demo: http://jsbin.com/copidifiji

That is the independent code from jQuery

if (window.addEventListener) {window.addEventListener('DOMMouseScroll', wheel, false); 
window.onmousewheel = document.onmousewheel = wheel;}

function wheel(event) {
    var delta = 0;
    if (event.wheelDelta) delta = (event.wheelDelta)/120 ;
    else if (event.detail) delta = -(event.detail)/3;

    handle(delta);
    if (event.preventDefault) event.preventDefault();
    event.returnValue = false;
}

function handle(sentido) {
    var inicial = document.body.scrollTop;
    var time = 1000;
    var distance = 200;
  animate({
    delay: 0,
    duration: time,
    delta: function(p) {return p;},
    step: function(delta) {
window.scrollTo(0, inicial-distance*delta*sentido);   
    }});}

function animate(opts) {
  var start = new Date();
  var id = setInterval(function() {
    var timePassed = new Date() - start;
    var progress = (timePassed / opts.duration);
    if (progress > 1) {progress = 1;}
    var delta = opts.delta(progress);
    opts.step(delta);
    if (progress == 1) {clearInterval(id);}}, opts.delay || 10);
}