Tryit Editor v2.7

Edit This Code:
<!DOCTYPE html>
<html>
<head>
<style>
.mystyle {
    width: 300px;
    height: 50px;
    text-align: center;
    background-color: coral;
    color: white;
    margin-bottom: 10px;
}
</style>

<script>
var _hmt = _hmt || [];
(function() {
var hm = document.createElement("script");
hm.src = "//hm.baidu.com/hm.js?73c27e26f610eb3c9f3feb0c75b03925";
var s = document.getElementsByTagName("script")[0];
s.parentNode.insertBefore(hm, s);
})();
</script>
</head>
<body>

<p>In this example, we first search for the element in the document with id="myDIV". Then, if this element has a class of "mystyle" - change its font size.</p>

<div id="myDIV" class="mystyle">
I am a DIV element
</div>

<button onclick="myFunction()">Try it</button>

<script>
function myFunction() {
    var x = document.getElementById("myDIV");
    
    if (x.className === "mystyle") { 
        x.style.fontSize = "30px";
    }
}
</script>

</body>
</html>