copy.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>点击复制</title>
</head>
<body>
        <h2>点击复制</h2>

        <button onclick="copyStr('ABCDEFGHIJKLMN')">复制</button>

        <input type="text">
        
        <script>
        function copyStr(val) {
            var input = document.createElement("input");
            input.value = val;
            input.readOnly = true
            document.body.appendChild(input);
            input.select();
            input.setSelectionRange(0, input.value.length)
            document.execCommand('Copy');
            document.body.removeChild(input);
            window.scrollTo(0, 0)
            alert('复制成功')
        }
        </script>
</body>
</html>