JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">	
	<link href="https://cdn.jsdelivr.net/npm/[email protected]/dist/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-gH2yIJqKdNHPEq0n4Mqa/HGKIhSkIHeL5AyhkYV8i59U5AR6csBvApHHNl/vI1Bx" crossorigin="anonymous">
	<link rel="stylesheet" href="js_style.css" />
	<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/js/bootstrap.bundle.min.js" integrity="sha384-A3rJD856KowSb7dwlZdYEkO39Gagi7vIsF0jrRAoQmDKKtQBHUuLZ9AsSv4jD4Xa" crossorigin="anonymous"></script>
	<script src="lesson25.js"></script>
</head>
<body>
	<div id="fragment_25" style="margin-top:50px;">
		<div class="container">
			<div class="row">
				<div class="col-lg-12">
					<form>
						<!-- <textarea id="textarea_25" cols="35" rows="5">море небо песок небо море небо</textarea><br><br> -->
						<!-- <input type="text" placeholder="Введите слово" id="input_word"> -->
						<input type="button" value="Найти" onclick="poiskFragment()" style="margin-bottom:20px;">
					</form>
					<div class="text_25">
						<h3 id="vivod_text"></h3><br>
						<h3 id="vivod_colvo"></h3>
					</div>
				</div>
			</div>
		</div>
	</div>
</body>
</html>

CSS

span{
  color:red;
}

JavaScript

function poiskFragment() {
	// body...
	var textArea = 'море небо песок небо море небо';
	var wordOut = 'небо';
	var outputText = document.getElementById('vivod_text');
	var i = 0;

	for(i; i < textArea.length; i++){
		var resStr = textArea.substr(i, wordOut.length);
		var zamenaSlova = textArea.replace(resStr,`<span>${resStr}</span>`);
		if (resStr == wordOut) {
			outputText.innerHTML = zamenaSlova;
		}
	}

}