JSFiddle - React, Tailwind, and code Playground

HTML

<div class="menu">
    <div id="menu-center">
        <ul>
            <li><a class="menu-active" href="#home">Home</a>

            </li>
            <li><a href="#portfolio">Portfolio</a>

            </li>
            <li><a href="#about">About</a>

            </li>
            <li><a href="#contact">Contact</a>

            </li>
        </ul>
    </div>
</div>
<section class="section" id="home"></section>
<section class="section" id="portfolio"></section>
<section class="section" id="about"></section>
<section class="section" id="contact"></section>

CSS

body, html {
    margin: 0;
    padding: 0;
    height: 100%;
    width: 100%;
}
.menu {
    width: 100%;
    height: 75px;
    background-color: rgba(0, 0, 0, 1);
    position: fixed;
    background-color:rgba(4, 180, 49, 0.6);
    -webkit-transition: all 0.3s ease;
    -moz-transition: all 0.3s ease;
    -o-transition: all 0.3s ease;
    transition: all 0.3s ease;
}
.light-menu {
    width: 100%;
    height: 75px;
    background-color: rgba(255, 255, 255, 1);
    position: fixed;
    background-color:rgba(4, 180, 49, 0.6);
    -webkit-transition: all 0.3s ease;
    -moz-transition: all 0.3s ease;
    -o-transition: all 0.3s ease;
    transition: all 0.3s ease;
}
#menu-center {
    width: 980px;
    height: 75px;
    margin: 0 auto;
}
#menu-center ul {
    margin: 15px 0 0 0;
}
#menu-center ul li {
    list-style: none;
    margin: 0 30px 0 0;
    display: inline;
}
.menu-active {
    font-family:'Droid Sans', serif;
    font-size: 14px;
    color: #fff;
    text-decoration: none;
    line-height: 50px;
}
a {
    font-family:'Droid Sans', serif;
    font-size: 14px;
    color: black;
    text-decoration: none;
    line-height: 50px;
}
#home {
    background-color: grey;
    height: 100%;
    width: 100%;
    overflow: hidden;
    background-image: url(images/home-bg2.png);
}
#portfolio {
    background-image: url(images/portfolio-bg.png);
    height: 100%;
    width: 100%;
}
#about {
    background-color: blue;
    height: 100%;
    width: 100%;
}
#contact {
    background-color: red;
    height: 100%;
    width: 100%;
}

JavaScript

const anchors = document.querySelectorAll('.menu li a');

 for (let anchor of anchors) {
   anchor.addEventListener('click', function (e) {
     e.preventDefault()
     
     const blockID = anchor.getAttribute('href');
     
     document.querySelector(blockID).scrollIntoView({
       behavior: 'smooth',
       block: 'center'
     })
   });
 }


 (function() {
  'use strict';

  var section = document.getElementsByTagName('section');
  var sections = {};
  var i = 0;

  Array.prototype.forEach.call(section, function(e) {
    sections[e.id] = e.offsetTop;
  });

  window.onscroll = function() {
    var scrollPosition = document.documentElement.scrollTop || document.body.scrollTop;

    for (i in sections) {
      if (sections[i] <= scrollPosition) {
        document.querySelector('.menu-active').setAttribute('class', ' ');
        document.querySelector('a[href*=' + i + ']').setAttribute('class', 'menu-active');
      }
    }
  };
})();