Question

我有一个报告，用户只允许选择过去3个月的选项，如下所示：

我想编写一个javaScript函数来实现这个目的。

我尝试的是：

function getLastMonths(n) {

    var months = new Array();

    var today = new Date();
    var year = today.getFullYear();
    var month = today.getMonth() + 1;

    var i = 0;
    do {
        months.push(year + (month > 9 ? "" : "0") + month);
        if(month == 1) {
            month = 12;
            year--;
        } else {
            month--;
        }
        i++;
    } while(i < n);

    return months;

}

然后我通过传递参数来调用函数：

document.write(getLastMonths(4));

打印：

201704,201703,201702,201701

这不是我要求的模式。

有人可以帮助我吗？

Answer 1

你可以这样做。只需继续从当前日期减去one month

＆＃13;

function getLastMonths(n) {
  var m =['January','February','March','April','May','June','July','August','September','October','November','December'];
  var last_n_months =[]
  var d = new Date()
  for(var i=0;i<n;i++){
    last_n_months[i] = m[d.getMonth()]+ ' - ' + d.getFullYear().toString()
    d.setMonth(d.getMonth()-1)
  }
  return last_n_months
}
console.log(getLastMonths(3))

＆＃13;

Answer 2

看看这里。由于 for loop

，它有点短

function getLast3Months() {

  var monthNames = ["January", "February", "March", "April", "May", "June",
    "July", "August", "September", "October", "November", "December"
  ];

  var today = new Date();
  var last3Months = []

  for (i = 0; i < 3; i++) {
    last3Months.push(monthNames[(today.getMonth() - i)] + ' - ' +today.getFullYear()  );
  }
  return last3Months;
}

document.write(getLast3Months());

Answer 3

试试这个。将月份名称添加到某些array中，然后找到索引

function getLastMonths(n) {
var m =['','Jan','Feb','Mar','Aprl','May','Jun','July','Aug','Sep','Oct','Nov','Dec'];
  var months = new Array();

  var today = new Date();
  var year = today.getFullYear();
  var month = today.getMonth()+1;

  var i = 0;
  do {
    months.push( m[parseInt((month > 9 ? "" : "0") + month)]+'-'+year);
    if (month == 1) {
      month = 12;
      year--;
    } else {
      month--;
    }
    i++;
  } while (i < n);

  return months;

}
document.write(getLastMonths(4));

Answer 4

由于内部JS名称不公开，您必须手动将号码转换为名称。

请参阅下面的工作示例。这将完全输出您在下拉列表中显示月份的方式。

var monthNames = ["January", "February", "March", "April", "May", "June",
      "July", "August", "September", "October", "November", "December"
];
function getLastMonths(n) {

    var months = new Array();

    var today = new Date();
    var year = today.getFullYear();
    var month = today.getMonth() + 1;

    var i = 0;
    do {
        months.push(monthNames[month] + ' - ' + year);
        if(month == 1) {
            month = 12;
            year--;
        } else {
            month--;
        }
        i++;
    } while(i < n);

    return months;

}

document.write(getLastMonths(4));

Answer 5

如何使用moment.js？

var getLastMonths = function(n) {
  var arr = new Array();

  arr.push(moment().format('YYYY MM'));

  for(var i=1; i< 3; i++){
    arr.push(moment().add(i*-1, 'Month').format('YYYY MM'));
  }
  
  return arr;
}

var appendOptions = function(arr) {
  var html = '';
  
  for(var i=0; i<arr.length; i++) {
    html += '<option value="' + arr[i] + '">' + arr[i] + '</option>'  
  }

  document.getElementById('select-months').innerHTML = html;

}

var months = getLastMonths(4);
appendOptions(months);

<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.18.1/moment.min.js"></script>

<select id="select-months"></select>

Answer 6

我已经修改了先前的代码并给出了一个示例：小提琴：https://jsfiddle.net/asutosh/rogpxwah/

function getLast3Months() {

  var monthNames = ["January", "February", "March", "April", "May", "June",
    "July", "August", "September", "October", "November", "December"
  ];

  var today = new Date(2019,3,12);
  var month=today.getMonth();
  var last3Months = []

  for (i = 0; i < 3; i++) {
      var newMonth=(today.getMonth() - i);
      var newYear=today.getFullYear();

      monthInWords=monthNames[newMonth];
      if(newMonth<0){

       newYear=today.getFullYear() - 1;
       monthInWords=monthNames[12+newMonth];
      }
     var newDate= new Date(today.getDate(), newMonth, newYear);
     last3Months.push(monthInWords + ' - ' +newYear  );
  }
  return last3Months;
}

window.document.write(getLast3Months());

Answer 7

以下是一个 Node 12+，ES2020 Generator 方法，代码少于 ~5 个节点...

function* lastMonths(start = 0, end = 4, step = 1, D = new Date()) {
  const o = new Intl.DateTimeFormat("en-US" , { month: "long", year: "numeric" })
  for (let i = start; i < end; i += step) {
    const past = new Date(D)
    void past.setMonth(D.getMonth() - i)
    const localeStr = o.format(past).replace(' ', ' - ')
    yield localeStr
  }
  return D
}
console.log([...lastMonths()])

<块引用>

[“7 月 - 2021 年”， “6 月 - 2021 年”， “5 月 - 2021 年”， “4 月 - 2021 年”]

来源：

在选择下拉列表中获取最近3个月的名称

7 个答案: