检查集合中的日期是3个月，6个月还是9个月（依此类推）

Question

必须使用moment.js检查项目集合是否包含已通过3、6等个月的startDate，但是在想出一种方法来计算今天与startDate之间的时间差时遇到了问题if (today / startDate) % 3 === 0但我认为这不是最好的方法，结果也不尽人意。 即使像使用moment.js diff一样，也不会产生期望的结果，并且记录显然还没有过去3、6等个月的项目。 显然我想念一些东西，希望能有所帮助，谢谢。

const today = moment()

const projects = await ProjectModel.find()
projects.forEach(project => {
    if (today.diff(moment(project.startDate), "month") % 3 == 0) {
        console.log(project)
    }
})

Answer 1

％是错误的处理方法。 您想找到日期所属的3个月前的括号，因此获得以月为单位的差值并除以3并得出结果。 如果diff <3，则为0。如果3 <= diff <6个月，则为1，依此类推。

例如

 let projects = [ {startDate: new Date(2017,10,1)}, // 1 Nov 2017 {startDate: new Date(2018,10,1)}, // 1 Nov 2018 {startDate: new Date(2019, 0,1)}, // 1 Jan 2019 {startDate: new Date(2019, 3,1)}, // 1 Apr 2019 {startDate: new Date(2019, 4,1)}, // 1 May 2019 {startDate: new Date(2019, 6,1)}, // 1 Jul 2019 {startDate: new Date(2019, 7,1)} // 1 Aug 2019 ]; let today = moment(); projects.forEach(project => { let diff = today.diff(moment(project.startDate), "month") / 3 | 0; console.log( moment(project.startDate).format('DD-MMM-YYYY') + ' was ' + (diff * 3) + ' to ' + (++diff * 3) + ' months ago' ); }) 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.24.0/moment.min.js"></script> 

Answer 2

模对我来说很有意义。 如果滚动自己的日期，它的工作原理如下（加上或减去一个leap日），这就是诸如moment.js之类的库很擅长抽象的东西：

 const projects = [ { id: 1, startDate: 1551441600000 }, { id: 2, startDate: 1554120000000 }, { id: 3, startDate: 1556712000000 }, { id: 4, startDate: 1559390400000 }, { id: 5, startDate: 1564660800000 } ]; // Gets current year, month, and date const now = new Date(), thisYear = now.getFullYear(), thisMonth = now.getUTCMonth(), thisDate = now.getUTCDate(); // Loops through projects projects.forEach(project => { // Gets year, month, and date for each project const then = new Date(project.startDate), startYear = then.getFullYear(), startMonth = then.getUTCMonth(), startDate = then.getUTCDate(); //console.log(then.toUTCString()); // Reports on the project if it started on an earlier day of the month 3, 6, etc months ago const justStarted = thisYear == startYear && thisMonth == startMonth, isQuarterInterval = thisMonth % 3 == startMonth % 3 && thisDate >= startDate if(isQuarterInterval && !justStarted){ console.log("Project #" + project.id + " started " + then); } });