计算身份证号最后一位

<button onclick="idcard()">计算</button>

function idcard() {
    var num = $("#id").val().toString();
    var arr = [7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2];
    var last = [1, 0, "X", 9, 8, 7, 6, 5, 4, 3, 2];
    var s = 0;
    for (var i = 0; i < arr.length; i++) {
        s = s + num[i] * arr[i];
    }
    var l = last[s % 11];//最后一位
    console.log(l)
}