JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id="term">
<button type="button" id="go">Go</button>
<div id="rez"></div>

JavaScript

$('#go').click(function(){
    var term = $('#term').val();
    var text = 'Планшет Apple iPad купить недорого';
    var newText = String(text).replace(
              new RegExp(term, "gi"),
              "<strong>$&</strong>");
    $('#rez').html(newText);      
});