W3Context Online Editor v1.1

<!DOCTYPE html>
<html>

<head>
    <title>class Attribute Example</title>
    <script>
        function m1() {
            var e = document.querySelectorAll(".c1,.c2,.c3");
            for(var i=0;i<e.length;i++){
            e[i].style.color = "white";
            e[i].style.backgroundColor = "#404040";
            e[i].style.padding = "20px";
            e[i].style.fontSize = "20pt";
            e[i].style.borderRadius = "5px";            
            }
        }
        function m2() {
            var e = document.querySelectorAll(".c1,.c2,.c3");
            for(var i=0;i<e.length;i++){
            e[i].style= "";          
            }
        }
        
    </script> 
</head>

<body>
    <p>class Attribute in JavaScript</p>
    <button onclick="m1();">Apply style</button>
    <button onclick="m2();">Remove style</button>
    <p class="c1">Hello w3context.</p>
    <p class="c2">Hello World!</p>
	<p class="c3">Hello HTML!</p>    
</body>
</html>