javascriptmouseeventmouselistenermousewheel

Smooth vertical scrolling on mouse wheel in vanilla javascript?

I am a huge fan for vanilla javascript, currently I am working on a project where I need to implement smooth scrolling on mouse wheel scroll. I want to implement this using vanilla JS. I found a jQuery snippet on doing some research which go like below.

$(window).on('mousewheel DOMMouseScroll', function(e) {
   var dir,
   amt = 100;

   e.preventDefault();
   if(e.type === 'mousewheel') {
     dir = e.originalEvent.wheelDelta > 0 ? '-=' : '+=';
   }
   else {
     dir = e.originalEvent.detail < 0 ? '-=' : '+=';
   }      

   $('html, body').stop().animate({
     scrollTop: dir + amt
   },500, 'linear');
});

Can anyone help me out as in how to implement a smooth scroll without using a helper library like jQuery or any other library.

There are many implementations that people have done in jQuery. But I want a best implementation that one can do in vanilla JS. That can implemented anywhere in React, Angular & Vue anywhere.

Solution

  • How about this:

    function init(){
	new SmoothScroll(document,120,12)
}

function SmoothScroll(target, speed, smooth) {
	if (target === document)
		target = (document.scrollingElement 
              || document.documentElement 
              || document.body.parentNode 
              || document.body) // cross browser support for document scrolling
      
	var moving = false
	var pos = target.scrollTop
  var frame = target === document.body 
              && document.documentElement 
              ? document.documentElement 
              : target // safari is the new IE
  
	target.addEventListener('mousewheel', scrolled, { passive: false })
	target.addEventListener('DOMMouseScroll', scrolled, { passive: false })

	function scrolled(e) {
		e.preventDefault(); // disable default scrolling

		var delta = normalizeWheelDelta(e)

		pos += -delta * speed
		pos = Math.max(0, Math.min(pos, target.scrollHeight - frame.clientHeight)) // limit scrolling

		if (!moving) update()
	}

	function normalizeWheelDelta(e){
		if(e.detail){
			if(e.wheelDelta)
				return e.wheelDelta/e.detail/40 * (e.detail>0 ? 1 : -1) // Opera
			else
				return -e.detail/3 // Firefox
		}else
			return e.wheelDelta/120 // IE,Safari,Chrome
	}

	function update() {
		moving = true
    
		var delta = (pos - target.scrollTop) / smooth
    
		target.scrollTop += delta
    
		if (Math.abs(delta) > 0.5)
			requestFrame(update)
		else
			moving = false
	}

	var requestFrame = function() { // requestAnimationFrame cross browser
		return (
			window.requestAnimationFrame ||
			window.webkitRequestAnimationFrame ||
			window.mozRequestAnimationFrame ||
			window.oRequestAnimationFrame ||
			window.msRequestAnimationFrame ||
			function(func) {
				window.setTimeout(func, 1000 / 50);
			}
		);
	}()
}
    p{
  font-size: 16pt;
  margin-bottom: 30%;
}
    <body onload="init()">
  <h1>Lorem Ipsum</h1>
  
  <p>Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.</p>
  
  <p>Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.</p>
  
  <p>Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.</p>
</body>

    Use it by calling new SmoothScroll(target,speed,smooth)

    Arguments:

    1. target: the element to be scrolled smoothly - can be a div or document
    2. speed: the amout of pixels to be scrolled per mousewheel step
    3. smooth: the smoothness factor, the higher the value, the more smooth.

    Thanks to @Phrogz for the mousewheel normalization.

    EDIT: Since Chrome 73 it is required to mark the event listener for the mousewheel event as non-passive in order to be able to call preventDefault() on it. Thanks to @Fred K for this.