Question

我的日期定义为"Jul 2015"或"Aug 2016"，我需要获得它们的去年版本。

例如：

getLastYear("Jul 2015")
return: Jul 2014

我如何在JavaScript中执行此操作？到目前为止，我的尝试无效：

var date = new Date('Jul 2015');
var new_date = new Date().setYear(date .getFullYear()-1);
alert(new_date );

// return a timestamp value e.g. 1404505003030

Answer 1

你几乎得到它，你错过了将timestamp转换为date

var date = new Date('Jul 2015');
var new_date = new Date().setYear(date .getFullYear()-1);
    new_date = new Date(new_date)

要设置日期格式，请使用：

var months = [
  "Jan", "Feb", "Mar",
  "Apr", "May", "Jun", "Jul",
  "Aug", "Sep", "Oct",
  "Nov", "Dec"
];


var monthIndex = new_date.getMonth();
var month = months[monthIndex]
var year = new_date.getYear();
var final_date = year + month
console.log(final_date) // you will get 'Jul 2014'

Answer 2

var date = new Date('Jul 2015');
date.setYear(date .getFullYear()-1);
alert(date);

应该为你做。 setYear返回一个值，并在日期上设置年份，因此您需要相应地使用它。

Answer 3

你需要做这样的事情，你可以根据你的要求编辑月份数组，

  function getLastYear(date){
  var month = new Array();
  month[0] = "January";
  month[1] = "February";
  month[2] = "March";
  month[3] = "April";
  month[4] = "May";
  month[5] = "June";
  month[6] = "July";
  month[7] = "August";
  month[8] = "September";
  month[9] = "October";
  month[10] = "November";
  month[11] = "December";
  var d = (new Date(new Date('1 '+date).setYear(new Date('1 '+date).getFullYear() -1)))
  console.log(d);
  return month[d.getMonth()]+' '+d.getFullYear()
}

getLastYear("July 2016") //"July 2015"

Answer 4

你实际上不需要日期对象。你也可以使用字符串函数：

var dateString = "Jul 2015";
var newString = dateString.substr(0,dateString.length - 4)+parseInt(dateString.substr(dateString.length - 4)-1);
alert(newString);

Answer 5

var date = new Date('Jul 2015');
var new_date = new Date(date .getFullYear()-1,date.getMonth());
var year = new_date.getFullYear();
Date.prototype.getMonthName = function() {
          var monthNames = [ "Jan", "Feb", "Mar", "April", "May", "Jun", 
                        "Jul", "Aug", "Sept", "Oct", "Nov", "Dec" ];
          return monthNames[this.getMonth()];
     }
var month  = new_date.getMonthName(new_date.getMonth());
alert(month+" "+year );

你也可以使用javascript的时刻库来转换为不同的格式http://momentjs.com/ reference:

JavaScript - 去年以特定格式获得同月

5 个答案: