JSFiddle - React, Tailwind, and code Playground

HTML

<div class="navbar">first content</div>
<div id="con">
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
</div>
<div id="example"></div>
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
    <p>abc</p><br />
</div>

CSS

body {
    background-color: #e3e3e3;
}
.navbar {
    position: fixed;
    top: 0px;
    width: 100%;
    height: 50px;
    background-color: bisque;
    border: 1px solid gray;
    margin: 0px;
    padding: 10px 0 0 10px;
}
#example {
    width: 100%;
    height: 50px;
    background-color: red;
    border: 1px solid gray;
    margin: 0px;
}

JavaScript

$(document).ready(function() {
    $(document).scroll(function() {
        if($( document ).scrollTop() >= $( "#example" ).offset().top && $( document ).scrollTop() < $( "#example" ).offset().top + 50) {
             $( ".navbar" ).text("second content");
        } else if($( document ).scrollTop() <= $( "#example" ).offset().top && $( document ).scrollTop() > $( "#example" ).offset().top - 50) {
            $( ".navbar" ).text("first content");
        }
    });
});