日期格式化方法封装，对外暴露使用

1）定义方法

//date.js
//前导0
export const addZero = function(n){
    return n >= 10 ? n : '0' + n
}
//时间对象格式化
export const dateFormat = function(date){
    return date.getFullYear() + "-" + addZero(date.getMonth()+1) + "-" + addZero(date.getDate()); 
}
/** 
* 获得相对当前周AddWeekCount个周的起止日期 
* AddWeekCount为0代表当前周   为-1代表上一个周   为1代表下一个周以此类推
* **/ 
export const getWeekStartAndEnd = function(AddWeekCount){
    //一天的毫秒数   
    var millisecond = 1000 * 60 * 60 * 24; 
    //获取当前时间   
    var currentDate = new Date();
    //相对于当前日期AddWeekCount个周的日期
    currentDate = new Date(currentDate.getTime() + (millisecond * 7 * AddWeekCount));
    //减去的天数   
    var minusDay = currentDate.getDay(); 
    //获得当前周的第一天   
    var currentWeekFirstDay = new Date(currentDate.getTime() - (millisecond * minusDay)); 
    //获得当前周的最后一天
    var currentWeekLastDay = new Date(currentWeekFirstDay.getTime() + (millisecond * 6));
    //起止日期数组   
    var startStop = new Array();    
    startStop.push(dateFormat(currentWeekFirstDay)); 
    startStop.push(dateFormat(currentWeekLastDay)); 
    return startStop; 
}
/** 
* 获得相对当月AddMonthCount个月的起止日期 
* AddMonthCount为0 代表当月 为-1代表上一个月  为1代表下一个月 以此类推
* ***/ 
export const getMonthStartAndEnd = function(AddMonthCount) { 
    //获取当前时间   
    var currentDate = new Date();
    var month = currentDate.getMonth() + AddMonthCount;
    if(month < 0){
        var n = parseInt((-month)/12);
        month += n*12;
        currentDate.setFullYear(currentDate.getFullYear()-n);
    }
    currentDate = new Date(currentDate.setMonth(month));
    //获得当前月份0-11   
    var currentMonth = currentDate.getMonth(); 
    //获得当前年份4位年   
    var currentYear = currentDate.getFullYear(); 
    //获得上一个月的第一天   
    var currentMonthFirstDay = new Date(currentYear, currentMonth,1); 
    //获得上一月的最后一天   
    var currentMonthLastDay = new Date(currentYear, currentMonth+1, 0);  
    //起止日期数组   
    var startStop = new Array(); 
    startStop.push(dateFormat(currentMonthFirstDay)); 
    startStop.push(dateFormat(currentMonthLastDay)); 
    //返回   
    return startStop;
}

　　2）使用封装方法：

import {dateFormat} from 'service/date'

var date = dateFormat(new Date())
console.log(date)    //2019-03-29