<!DOCTYPE html>
<html>
<head>
<script src="http://www.sargonco.com/Uploads/Public/article/webdistut/javascript/jquery-3.2.1.min.js"></script>

<script>
$(document).ready(function(){
    $("#btn1").click(function(){
        $("#test1").text(function(i, origText){
            return "Old text: " + origText + " New text: Hello world! (index: " + i + ")";
        });
    });

    $("#btn2").click(function(){
        $("#test2").html(function(i, origText){
            return "Old html: " + origText + " New html: Hello <b>world!</b> (index: " + i + ")";
        });
    });
});
</script>
</head>
<body>

<p id="test1">This is a <b>bold</b> paragraph.</p>
<p id="test2">This is another <b>bold</b> paragraph.</p>

<button id="btn1">Show Old/New Text</button>
<button id="btn2">Show Old/New HTML</button>

</body>
</html>

This is a bold paragraph.

This is another bold paragraph.