js日期插件dateHelp获取本月、三个月、今年的日期_javascript技巧

var myDate = new DateHelp({
date:'2015-02-01',//从此日期开始计算
format:'yyyy/MM/dd'
});

myDate.getThisMonth();
myDate.getThreeMonth();
myDate.getThisYear();

/**
 * 通过调用可以获取本月，近三个月，今年的日期
 * @param obj
 * @constructor
 */
function DateHelp(obj) {
 /*var obj = {
  date:'2015-02-01',//从此日期开始计算
  type:'month',//以年月日向前计算：年（year），月（month），日（day）
  value:'14',//向前计算的数值，年月日
  format:'yyyy/mm/dd'//日期格式
  }*/

 this.date = obj.date;
 this.type = obj.type;
 this.value = obj.value == undefined ? obj.value : 0;
 this.format = obj.format == undefined ? obj.format: 'yyyy/MM/dd';

 //日期和非日期格式获取年月日
 if (this.date instanceof Date){
  //处理传进来的是日期函数的

  this.year = this.date.getFullYear();
  this.month = this.date.getMonth()+1;
  this.day = this.date.getDate();
 }else{
  //处理传入的是非日期函数的

  this.year = this.date.substr(0, 4);
  this.month = this.date.substr(5, 2);
  this.day = this.date.substr(8, 2);
 }

}

DateHelp.prototype.beforeDate = function(type, value){

 var _type = type || this.type,
  _value = value || this.value,
  _year = this.year,
  _month = this.month,
  _day = this.day;

 if (_type == 'year' || _type == '年'){
  _year -= _value;
 }else if (_type == 'month' || _type == '月'){
  _year -= parseInt(_value / 12);
  _month -= _value % 12;
  if(_month <= 0){
   _year -= 1;
   _month += 12;
  }
 }else if (_type == 'day' || _type == '日'){

 }else {

 }

 var date = new Date(_year, _month - 1, _day)
 return this.formatDate(date, this.format);
}

DateHelp.prototype.formatDate = function(date,fmt){

 var o = {
  "M+" : date.getMonth()+1,     //月份
  "d+" : date.getDate(),     //日
  "h+" : date.getHours(),     //小时
  "m+" : date.getMinutes(),     //分
  "s+" : date.getSeconds(),     //秒
  "q+" : Math.floor((date.getMonth()+3)/3), //季度
  "S" : date.getMilliseconds()    //毫秒
 };
 if(/(y+)/.test(fmt))
  fmt=fmt.replace(RegExp.$1, (date.getFullYear()+"").substr(4 - RegExp.$1.length));
 for(var k in o)
  if(new RegExp("("+ k +")").test(fmt))
   fmt = fmt.replace(RegExp.$1, (RegExp.$1.length==1) ? (o[k]) : (("00"+ o[k]).substr((""+ o[k]).length)));
 return fmt;
}

DateHelp.prototype.getThisMonth = function() {

 var first = new Date(this.year, this.month - 1);
 var last = new Date(this.year, this.month, 0);

 return this.formatDate(first, this.format) + " - " + this.formatDate(last, this.format);
}

DateHelp.prototype.getThreeMonth = function() {

 return this.beforeDate('month', 3) + " - " + this.beforeDate('day', 0);
}

DateHelp.prototype.getThisYear = function() {

 var first = new Date(this.year, 0, 1);
 var last = new Date(this.year, 11, 31);

 return this.formatDate(first, this.format) + " - " + this.formatDate(last, this.format);
}


/*
//示例
var myDate = new DateHelp({
 date:'2015-02-01',//从此日期开始计算
 format:'yyyy/MM/dd'
});

console.log(myDate.getThisMonth());
console.log(myDate.getThreeMonth());
console.log(myDate.getThisYear());*/