lottery.html

<html>

<head>
    <meta name="viewport" content="initial-scale=1" />
    <style>
        html {
            width: 100%;
            height: 100%;
        }

        * {
            border: 0px;
            font-size: 20px;
            line-height: 30px;
        }

        textarea {
            width: 100%;
            height: 300px;
            background: #222;
            color: #eee;
        }

        button {
            width: 100%;
            height: 30px;
            background: #666;
        }
    </style>
</head>

<body>
    <textarea placeholder="每一行為籤名" id="r"></textarea>
    <button onclick="start()">抽籤</button>
    <script>
        var r = document.getElementById("r");

        function start() {
            var rs = r.value.split("\n").filter(function (v) {
                    return !!v;
                }),
                idx = (Math.random() * rs.length) | 0;
            alert(rs[idx]);
            rs.splice(idx, 1);
            r.value = rs.join("\n");
        }
    </script>
</body>

</html>