JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li><a href="#">Link 1</a></li>
    <li><a href="#" class="active">Link 2</a></li>
    <li><a href="#">Link 3</a></li>
    <li><a href="#">Link 4</a></li>
    <li><a href="#">Link 5</a></li>
</ul>

CSS

li {
    float: left;
}
li a {
    display: block;
    padding: 10px 10px 10px 25px;
    background: #4563DC;
    color: #111;
    position: relative;
}
li a.active {
    background: coral;
    color: #EEE;
}
li a:before, li a:after {
    position: absolute;
    top: 0;
    left: 0;
    content:'';
    width: 0px;
    height: 0px;
    border-style: solid;
    border-width: 40px 14px 0 0;
    border-color: #4563DC transparent transparent transparent;
    z-index: 1;
}
li a:after {
    left: auto;
    right: -14px;
    z-index: 2;
}
li a.active:after {
    border-top-color: coral;
}
li:first-of-type a:before {
    border-top-color: #FFF;
}

JavaScript

var $a = $('a').click(function(e) {
    e.preventDefault();
    $a.removeClass('active');
    $(this).addClass('active');
});