JSFiddle - React, Tailwind, and code Playground

HTML

<button onclick="highlight('fox')">Highlight</button>
<div id="inputText">The fox went over the fence</div>

CSS

.highlight {
    background-color:yellow;
}

JavaScript

window.highlight = function(text) {
    var inputText = document.getElementById("inputText");
    var innerHTML1 = inputText.innerHTML;
    var index = innerHTML1.indexOf(text);
    if (index >= 0) {
        innerHTML1 = innerHTML1.substring(0, index) + "<span class='highlight'>" + "Fynn the fox" + "</span>" + innerHTML1.substring(index + text.length);
        inputText.innerHTML = innerHTML1;

    }

}