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>
     
</div>

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);
debugger;
    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;
    if( e.originalEvent.wheelDelta >= 0) {
      currentAnchor = scrollUpDown('up');
      console.log('вверх');
    } else {

      currentAnchor = scrollUpDown('down');
      console.log('вниз')
    }

    isAnimating  = true;
    $('html, body').animate({
        scrollTop: currentAnchor
    }, 500, 'swing', function(){
        isAnimating  = false;
    });
  });

});