JSFiddle - React, Tailwind, and code Playground

by zav19791979

HTML

<script src="https://code.jquery.com/jquery-3.2.1.min.js"></script>
<div id="s1">
  Секция 1
  <a href="#s2">Вниз</a>
</div>
<div id="s2">
  Секция 2
  <a href="#s1">Вверх</a>
  
  <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Beatae, minima, quae. Nemo iste eveniet necessitatibus quas deleniti. Et deleniti nemo hic delectus minus quia, incidunt laudantium consequuntur, harum dolorem reiciendis.</p>
  
   <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Beatae, minima, quae. Nemo iste eveniet necessitatibus quas deleniti. Et deleniti nemo hic delectus minus quia, incidunt laudantium consequuntur, harum dolorem reiciendis.</p>
   
    <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Beatae, minima, quae. Nemo iste eveniet necessitatibus quas deleniti. Et deleniti nemo hic delectus minus quia, incidunt laudantium consequuntur, harum dolorem reiciendis.</p>
    
     <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Beatae, minima, quae. Nemo iste eveniet necessitatibus quas deleniti. Et deleniti nemo hic delectus minus quia, incidunt laudantium consequuntur, harum dolorem reiciendis.</p>
     
       <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Beatae, minima, quae. Nemo iste eveniet necessitatibus quas deleniti. Et deleniti nemo hic delectus minus quia, incidunt laudantium consequuntur, harum dolorem reiciendis.</p>
  
   <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Beatae, minima, quae. Nemo iste eveniet necessitatibus quas deleniti. Et deleniti nemo hic delectus minus quia, incidunt laudantium consequuntur, harum dolorem reiciendis.</p>
   
    <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Beatae, minima, quae. Nemo iste eveniet necessitatibus quas deleniti. Et deleniti nemo hic delectus minus quia, incidunt laudantium consequuntur, harum dolorem reiciendis.</p>
    
     <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Beatae, minima, quae. Nemo iste...

CSS

body {
  margin: 0;
  padding: 0;
}

div {
  width: 100%;
  height: 300px;
  padding-top: 10px;
  padding-left: 20px;
  box-sizing: border-box;
  color: #ffffff;
}

#s1 {
  background-color: #ff8080;
}

a {
  display: block;
  margin-top: 50px;
}

#s1 {
  min-height: 100vh;
}

body {
  background-color: #eee;
}

p {
  color: #000;
}

JavaScript

var currentAnchor = 0;
var isAnimating  = false;

function scrollUpDown(dir) {

  var sections = $('#s1, #s2');
  var currentScroll = $(document).scrollTop();
  var nearestEl = null;
  var defaultTop = 0;

  sections.each(function(i, el) {

    var el = $(el);

    if (dir == 'down') {
      if (currentScroll < el.offset().top) {
        if (nearestEl != null && nearestEl.offset().top > el.offset().top) {
          nearestEl = el;
        } else if (nearestEl == null) {
          nearestEl = el;
        }
      }
      defaultTop = $(document).outerHeight(true);
    }

    if (dir == 'up') {
      if (currentScroll > el.offset().top) {
        if (nearestEl != null && nearestEl.offset().top < el.offset().top) {
          nearestEl = el;
        } else if (nearestEl == null) {
          nearestEl = el;
        }
      }
      var defaultTop = 0;
    }

  });

  if (nearestEl != null) {
    return(nearestEl.offset().top);
  } else {
    return(defaultTop);
  }
}

$(function(){

$('body').on('mousewheel', function(e){

				e.preventDefault();
				e.stopPropagation();

				if( isAnimating ) {
					return false;
				}

				isAnimating  = true;
				currentAnchor = null; // сбрасываем метку перехода
				if( e.originalEvent.wheelDelta >= 0) {
					currentAnchor = scrollUpDown('up');
					console.log('вверх');
				} else {

					var firstSectionHeight = $('#s1').outerHeight(); // высота первого блока
					var documentScroll = $(document).scrollTop(); // общий скролл
					if(documentScroll < firstSectionHeight) { // если мы еще не промотали первый блок, включаем нашу прокрутку
						currentAnchor = scrollUpDown('down');
						console.log('вниз')
					}
				}

				if (currentAnchor) { // если прокрутка была не нужна, метки перехода нет и переход не производим
					isAnimating  = true;
					$('html, body').animate({
						scrollTop: currentAnchor
					}, 500, 'swing', function() {
						isAnimating = false;
					});
				} else {
					isAnimating  = false;
				}
			});

});