js gets the date codes before and after the specified date_javascript skills

function getmonths(dateday){
/*Get the current date Month*/
var curDate = new Date(dateday);
return curDate.getMonth() 1;
};
function getYears(dateday){
/*Get the year of the current date */
var curDate = new Date(dateday);
return curDate.getFullYear();
};
function getCountDays(dateday) {
/*Conversion time*/
var curDate = new Date(dateday);
/* Get the current month*/
var curMonth = curDate.getMonth();
/* Generate the actual month: Since curMonth will be 1 smaller than the actual month, Therefore, 1 needs to be added */
curDate.setMonth(curMonth 1);
/* Set the date to 0 */
curDate.setDate(0);
/* Return the number of days in the current month*/
return curDate.getDate();
};
/*
Get yesterday’s start time, the default is 1 day, the default is not to return a short time
day: start time
amount: the number of days apart
isShortTime: whether to display short time
*/
function getBeforeDay(day,amount,isShortTime){
if(Date.parse(day) != Date.parse(day )){
return false;
}
var days = new Date(new Date(day)-1000*60*60*24);
if(amount){
var number = parseInt(amount);
if(number && number > 0 && !isNaN(number)){
days = new Date(new Date(day)-1000*60*60*24*number);
}
}
return dateFormat(days,isShortTime);
}
/*
Get the start time tomorrow, the default is 1 day, the default is not to return a short time
day: start time
amount: number of days apart
isShortTime: whether to display short time
*/
function getAfterDay(day,amount,isShortTime){
if(Date.parse(day ) != Date.parse(day)){
return false;
}
day =new Date(day);
var v = day.valueOf();
var days = new Date((v 86400000));
if(amount){
var number = parseInt(amount);
if(number && number > 0 && !isNaN(number)){
days = new Date((v 86400000*number));
}
}
return dateFormat(days,isShortTime);
}
/*
Format time, the default is Do not return short time
day : Date
isShortTime : Whether to display short time
*/
function dateFormat(day,isShortTime){
if(Date.parse(day) != Date. parse(day)){
return false;
}
var days = new Date(day);
if(isShortTime && isShortTime==true){
var hours = days.getHours ()<10?"0" days.getHours():days.getHours();
var minutes = days.getMinutes()<10?"0" days.getMinutes():days.getMinutes() ;
var seconds = days.getSeconds()<10?"0" days.getSeconds():days.getSeconds();
return days.getFullYear() "-" (days.getMonth() 1 ) "-" days.getDate() " " hours ":" minutes ":" seconds;
}else{
return days.getFullYear() "-" (days.getMonth() 1) "-" days.getDate();
}
}