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js 获取当前年是第几周,从那天到那天

夏立军5年前 (2020-11-30)JavaScript859

## 内置两个不同的方法
> 第一个为当前周范围
> 第二个为当年第几周

```javascript
        var now = new Date()
        var weekFirstDay = new Date(now - (now.getDay() - 1) * 86400000)
        var firstMonth = Number(weekFirstDay.getMonth()) + 1
        var weekLastDay = new Date((weekFirstDay / 1000 + 6 * 86400) * 1000)
        var lastMonth = Number(weekLastDay.getMonth()) + 1

var currentWeek = weekFirstDay.getFullYear() + '-' + firstMonth + '-' + weekFirstDay.getDate() + '~' + weekLastDay.getFullYear() + '-' + lastMonth + '-' + weekLastDay.getDate()

console.log(currentWeek);

//计算本年的周数
        function getYearWeek(endDate) {
            //本年的第一天
            var beginDate = new Date(endDate.getFullYear(), 0, 1);
            //星期从0-6,0代表星期天，6代表星期六
            var endWeek = endDate.getDay();
            if (endWeek == 0) endWeek = 7;
            var beginWeek = beginDate.getDay();
            if (beginWeek == 0) beginWeek = 7;
            //计算两个日期的天数差
            var millisDiff = endDate.getTime() - beginDate.getTime();
            var dayDiff = Math.floor((millisDiff + (beginWeek - endWeek) * (24 * 60 * 60 * 1000)) / 86400000);
            return Math.ceil(dayDiff / 7) + 1;
        }

var date = new Date();
        var year = date.getFullYear();
        var week = getYearWeek(date);
        var yearWeek = year + "年" + (week > 9 ? week : "0" + week) + "周";
        console.log(yearWeek);
```

## 结果
![](http://typecho.128x.cn/2020/11/202011304582_4822.png)