//根据长度生成随机码
app.randCode = function (len) {
    var charset = ‘abcdefghkmnprstuvwxyzABCDEFGHKMNPRSTUVWXYZ0123456789‘;
    var charsetLen = charset.length - 1;
    var code = ‘‘;
    for (var i = 0; i < len; i++) {
        code += charset[parseInt(charsetLen * Math.random())];
    }
    return code;
};