Examples of how to add text in a html page using javascript:
Table of contents
Add text using innerHTML
<!DOCTYPE html>
<html lang="en" dir="ltr">
<head>
<meta charset="utf-8">
<title></title>
</head>
<body>
<div id="intro">
<h1>Learning Javascript</h1>
<p>First paragraph</p>
</div>
<script>
document.querySelector("#intro").innerHTML +=
"<p>Second paragraph</p>";
</script>
</body>
</html>
Add text using creating elements and text nodes
Another solution is (see Document.createTextNode())
<!DOCTYPE html>
<html lang="en" dir="ltr">
<head>
<meta charset="utf-8">
<title></title>
</head>
<body>
<div id="intro">
<h1>Learning Javascript</h1>
<p>First paragraph</p>
</div>
<script>
var mytag = document.createElement('p');
var mytext = document.createTextNode('Second paragraph');
mytag.appendChild(mytext);
var div = document.querySelector("#intro");
div.appendChild(mytag);
</script>
</body>
</html>