Lucky roll

请写一个抽奖程序，已有参与抽奖的员工工号组成的数组 staffIds。
规则1：同一员工不可重复中奖
规则2：每轮执行抽奖程序，入参是本轮要抽取的中奖人数n，将中奖人工号打印出来

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Lucky roll</title>
</head>
<body>
<button onclick="onClear()"> Clear</button>
<br/>
<textarea name="staffids" id="staffids" cols="30" rows="10" placeholder="please input employeeid"></textarea>
<br/>
<textarea name="numroll" id="numroll" cols="30" rows="10" placeholder="please input number to win,be less than the NO of employees"></textarea>
<br/>
<button onclick="onRoll()">Roll</button>
<br/>
<input type="text" id="rollresult" placeholder="winnerlist"/>

<script>
    var pool =[];
    var exWinners = new Set([]);
    function onClear() {
        document.getElementById("employeeid").value='';
        document.getElementById("rollresult").value='';
        document.getElementById("numroll").value = '';
        exWinners.clear();
        alert("All the staffids have been cleared");
    }
    function onRoll() {
        staffids=document.getElementById("staffids").value.split(",");
        console.log(staffids);
        const count= parseInt(document.getElementById("numroll").value);
        console.log(count);
        pool =different(staffids,exWinners)
        console.log("pool"+pool);
        if (pool.length ==0){
            alert("all the employees have been selected")
        }
        shuffle(pool);
        var winner = pool.slice(0,count);
        for (var i=0;i<winner.length;i++){
            exWinners.add(winner[i]);
        }
        document.getElementById("rollresult").value= winner.join(",");

    }
    function different(staffids,exWinners) {
        var res=[];
        res = staffids.filter(x=>!exWinners.has(x));
        return res;
    }
    function shuffle(arr){
        arr.sort(()=>{
            return  Math.random() > 0.5 ? -1 : 1;
            //返回值大于0，表示需要交换；小于等于0表示不需要交换
        })
    }

    </script>
    </body>
    </html>