好久没写博客了最近遇到了一个比较有意思的功能点 花了一天半的时间才弄出来
难点：
1、获取周和天感觉不难就不讨论了 后面会写实现的核心代码
2、每个月的天数都不一样怎么办?
3、上一年到下一年的过度阶段要注意。
话不多说上代码
天 输入num为 1昨天 2前天 …
function getDay (num){if(num<=0) return;let day = new Date();let y_start = new Date(day.getTime()-24*60*60*1000*num);let y_end = new Date(day.getTime()-24*60*60*1000*(num-1));let y_start_obj={year:y_start.getFullYear(),month:y_start.getMonth()+1 >= 10 ? y_start.getMonth()+1 : '0'+(y_start.getMonth()+1),day:y_start.getDate() >= 10 ? y_start.getDate() : '0'+y_start.getDate()};let y_end_obj={year:y_end.getFullYear(),month:y_end.getMonth()+1 >= 10 ? y_end.getMonth()+1 : '0'+(y_end.getMonth()+1),day:y_end.getDate() >= 10 ? y_end.getDate() : '0'+y_end.getDate()};return [`${y_start_obj.year}-${(y_start_obj.month)}-${y_start_obj.day} 00:00:00`,`${y_end_obj.year}-${(y_end_obj.month)}-${y_end_obj.day} 00:00:00`];
}
周 num为1表示上周 2上上周 3上上上周 …
function getWeek (num) {if(num<=0) return;let one_day = 24*60*60*1000;//1知道今天是周几 0~6 周日~周六;let today = new Date();let what_day = today.getDay(); if(what_day===0) what_day = 7 ;//以周一作为一周的开始 周日作为一周的结束//2获取本周的周一日期，这样上周就是周一的前七天 let Monday = new Date(today.getTime()-one_day*(what_day-1));//3获取上周或上好几周的开始结束日期let week_start = new Date(Monday.getTime() - one_day*7*num);let week_end = new Date(Monday.getTime() - one_day*7*(num-1))let week_start_obj = {year:week_start.getFullYear(),month:week_start.getMonth()+1 >= 10 ? week_start.getMonth()+1 : '0'+(week_start.getMonth()+1),day:week_start.getDate() >= 10 ? week_start.getDate() : '0'+week_start.getDate()};let week_end_obj = {year:week_end.getFullYear(),month:week_end.getMonth()+1 >= 10 ? week_end.getMonth()+1 : '0'+(week_end.getMonth()+1),day:week_end.getDate() >= 10 ? week_end.getDate() : '0'+week_end.getDate()}return [`${week_start_obj.year}-${week_start_obj.month}-${week_start_obj.day} 00:00:00`,`${week_end_obj.year}-${week_end_obj.month}-${week_end_obj.day} 00:00:00`];
}
月 num为1表示上月 2表示上上月 …
function getMonth (num){if(num<=0) return;let today = new Date();let year = today.getFullYear();//当前年份let need_year = year - Math.floor(num/12);//获取到想要查询月所在的年份let need_year_next = need_year;//获取到想要查询月下一个月所在的年份let month = today.getMonth()+1;//获取到当前月//获取num 的余数 如果余数大于等于当前月份 则年份还要减1let num_remainder = num%12; if(num_remainder>=month){need_year--;need_year_next--;month += 12;}//获取到所需要的月份和所需要的月份的下一个月let need_month = month - num_remainder;let need_month_next = need_month + 1;//如果所需要月份的下一个月大于12 则需要调到下一年的一月if(need_month_next>12){need_month_next = 1;need_year_next++;}if(need_month===0) need_month = 12;//所需月份小于10 则前面补0if(need_month<10) need_month = '0'+need_month;if(need_month_next<10) need_month_next = '0'+need_month_next;return [`${need_year}-${need_month}-01 00:00:00`,`${need_year_next}-${need_month_next}-01 00:00:00`];
}