To add class, use forEach() along with classList.add().
Example
Following is the code −
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<link rel="stylesheet"
href="//code.jquery.com/ui/1.12.1/themes/base/jquery-ui.css">
<script src="https://code.jquery.com/jquery-1.12.4.js"></script>
<script src="https://code.jquery.com/ui/1.12.1/jquery-ui.js"></script>
<style>
.demo1 {
color: yellow;
}
.demo2 {
color: skyblue;
}
</style>
<body>
<ul>
<li>Javascript</li>
<li>MySQL</li>
<li>Java</li>
<li>MongoDB</li>
</ul>
</body>
<script>
addingClassUsingJavascript();
function addingClassUsingJavascript() {
const all = document.querySelectorAll('li');
all.forEach(function (t, i) {
if (i === 1) {
t.classList.add('demo1');
} else if (i === 2) {
t.classList.add('demo2');
}
});
}
</script>
</html>To run the above program, save the file name anyName.html(index.html). Right click on the file and select the option “Open with live server” in VS Code editor.
Output
This will produce the following output −
