// 生成随机字符串
function randomMixed(n) {
    var chars = [‘0‘, ‘1‘, ‘2‘, ‘3‘, ‘4‘, ‘5‘, ‘6‘, ‘7‘, ‘8‘, ‘9‘, ‘A‘, ‘B‘, ‘C‘, ‘D‘, ‘E‘, ‘F‘, ‘G‘, ‘H‘, ‘I‘, ‘J‘, ‘K‘, ‘L‘, ‘M‘, ‘N‘, ‘O‘, ‘P‘, ‘Q‘, ‘R‘, ‘S‘, ‘T‘, ‘U‘, ‘V‘, ‘W‘, ‘X‘, ‘Y‘, ‘Z‘];
    var res = "";
    for (var i = 0; i < n; i++) {
        var id = Math.ceil(Math.random() * 35);
        res += chars[id];
    }
    return res;
}

//alert(randomMixed(5))

// 更新验证码图片
function changeVerificationImg(imgId) {
    var newVerificationImg = app.url + ‘/Verifications/show?‘ + randomMixed(12);
    $(‘#‘ + imgId).attr(‘src‘, newVerificationImg);
}

js随机生成一个数组中的随机字符串以及更新验证码