以一个日期为中心点，生成前后一周的数据

根据一个需求，需要做一个功能：
 根据传入的一个json(日期，年份，月数，星期)，来生成以此为中心点的前后一周的数据。
该版本的JS 暂时不知处无参数传入，后续待优化。
PS:如图，红圈标记出来就是我们传入的值，上下为生成的对应数据

JS完整代码如下：

//  需要传入的json  格式
var json = {
    year: 2017,
    month: 12,
    weekday: '周六',
    day: 1
}
var calendar = {
    //  传入任意一个数，生成以该数为中心的，前后三天（共七天的数组）
    //  支持年，月，日，星期 四个数据的输出
    montharr: [],   //月份数组
    arr: [],      //存储前后七天的数组
    calendar_sign: 0,
    init: function () {
        calendar.arr[3] = json;
        calendar.arr.length = 7;
        calendar.judgeDay(json);  //模拟json 数据，
        console.log(calendar.arr)

    },
    // 判断星期
    judgeWeek: function (week) {
        var weekday = '';
        if (typeof week == 'string') {
            switch (week) {
                case  '周日':
                    weekday = 0;
                    break;
                case  '周一':
                    weekday = 1;
                    break;
                case  '周二':
                    weekday = 2;
                    break;
                case  '周三':
                    weekday = 3;
                    break;
                case  '周四':
                    weekday = 4;
                    break;
                case   '周五':
                    weekday = 5;
                    break;
                case  '周六':
                    weekday = 6;
                    break;
                default :
                    break;
            }
            return Number(weekday);
        }
        else {
            switch (week) {
                case  0:
                    weekday = '周日';
                    break;
                case  1:
                    weekday = '周一';
                    break;
                case  2:
                    weekday = '周二';
                    break;
                case  3:
                    weekday = '周三';
                    break;
                case  4:
                    weekday = '周四';
                    break;
                case  5:
                    weekday = '周五';
                    break;
                case  6:
                    weekday = '周六';
                    break;
                default :
                    break;
            }
            return weekday;
        }

    },
    judgeDay: function (json) {
        calendar.judgeMonth(json.year);
        var add = 0, reduce = 0;
        for (var i = 0; i < 7; i++) {
            var temJson = {};
            var weekNum=calendar.judgeWeek(json.weekday);
            if (i == 3) {
                calendar.arr[3].sign=0;
            } else {
                // 判断中心日期 前后日年月星期数据
                if (i < 3) {
                    temJson.day = json.day - (i + 1);
                    temJson.year = json.year;
                    if (temJson.day < 1) {
                        temJson.month = json.month - 1;
                        if (temJson.month < 1) {
                            temJson.year = json.year - 1;
                            temJson.month = 12;
                        }
                        temJson.sign = calendar.calendar_sign - 1;
                        reduce++;
                        temJson.day = calendar.montharr[temJson.month - 1] - reduce + 1;
                    } else {
                        temJson.month = json.month;
                        temJson.sign = calendar.calendar_sign;
                    }
                    var weekday=calendar.judgeWeek(Math.abs(weekNum-(i+1)+7)%7);
                    temJson.weekday=weekday;
                    calendar.arr[3 - i - 1] = temJson;
                } else if (i > 3) {
                    temJson.day = json.day + (i - 3);
                    temJson.year = json.year;
                    if (temJson.day > calendar.montharr[json.month - 1]) {
                        temJson.month = json.month + 1;
                        if (temJson.month > 12) {
                            temJson.month = 1;
                            temJson.year = json.year + 1;
                        }
                        temJson.sign = calendar.calendar_sign + 1;
                        add++;
                        temJson.day = add;
                    } else {
                        temJson.month = json.month;
                        temJson.sign = calendar.calendar_sign

                    }
                    var weekday=calendar.judgeWeek((weekNum+(i-3))%7);
                    temJson.weekday=weekday;
                    calendar.arr[3 + i - 3] = temJson;
                }

            }

        }

    },
    //判断每月天数
    judgeMonth: function (year) {
        if (calendar.judgeYear(year)) {
            calendar.montharr = [31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
        } else {
            calendar.montharr = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
        }
    },

    //判断闰年
    judgeYear: function (year) {
        return (year % 4 == 0) && (year % 100 != 0 || year % 400 == 0)
    }

}