document.getElementsByClassName(className)

The getElementsByClassName() method returns an HTMLCollection of every element that possesses the specified class.

EXAMPLE

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Class‑search – demo</title>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    
    <style>
        body {
            font-family: Arial, sans-serif;
            padding: 16px;
        }
        button {
            margin: 6px 0;
            padding: 6px 12px;
            font-size: 14px;
        }
        .highlight {
            margin: 4px 0;
            padding: 12px;
            border: 2px solid red;
            border-radius: 12px;
        }
        pre {
            padding: 8px;
            border: 1px solid #ccc;
            white-space: pre-wrap;
        }
    </style>
</head>
<body>
    <h1>Class‑search</h1>

    <p class="highlight">First highlighted paragraph.</p>
    <p class="highlight">Second highlighted paragraph.</p>
    <p>Unstyled paragraph.</p>

    <button id="btnFind">List all elements with class “highlight”</button>
    <pre id="out"></pre>

    <script>
        document.getElementById("btnFind").onclick = function () {
            const elems = document.getElementsByClassName("highlight");
            let txt = `Found elements with class "highlight" (${elems.length}):\n`;
            for (let i = 0; i < elems.length; i++) {
                txt += `  #${i+1}: ${elems[i].textContent}\n`;
            }
            document.getElementById("out").textContent = txt;
        };
    </script>
</body>
</html>

RESULT