Live Demo - Javascript getElementsByTagName

Source Code

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8">
    <title>JavaScript Select Elements by Tag Name</title>
</head>
<body>
 <h1>JavaScript Select Elements by Tag Name</h1>
   <script type="text/javascript">  
function displayInfo(){  
var totalElements=document.getElementsByTagName("p");  

 for(var elem in totalElements) {  
        totalElements[elem].style.background = "lightgrey";
        totalElements[elem].style.padding = "10px";
        totalElements[elem].style.fontSize = "20px"; 
    } 
  
}  
</script> 
<p>This is a first pragraph eelemetn.</p>  
<p>This is another paragraph element.</p>  
<p>Let's use the above concept.</p>  
<button onclick="displayInfo()">count paragraph</button>
</body>
</html>

Source Code

Source Code Output :Running