如何在Javascript中将日期向前滚动到指定的日期？

Question

I'm working on a form that needs to automatically calculate the day the form is being submitted in the format ('MMDDYYYY'), and then on the click of one of two links a link, calculate the closest first day of the coming month, and the closest 15th day of the coming month.

I already created a script that pulls in the date and outputs it to a variable in the format I need, but I need help in calculating the roll forward.

Here's an example of the logic I'm thinking I need:

If the current date is 04092013, on a the button press labeled "Coming 1st of Month" a variable value of 05012013 would be calculated.

If the current date is 04092013, on a button press labeled "Coming 15th of Month" a variable value of 04152013 would be calculated.

If the current date is 04162013 or any date up to the end of the current month, on a button press labeled "Coming 15th of Month" a variable value of 05152013 would be calculated.

Answer 1

Look at the Date object, it should provide what you need:

https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Date

For example something like this for your first 2 buttons:

$(function() {
    var date = new Date(2013, 10, 24);

    $("#date").html(date.toString());
    $("#date1").html((new Date(date.getYear(), date.getMonth()+1, 1)).toString());
    $("#date2").html((new Date(date.getYear(), date.getMonth()+1, 15)).toString());
});

(Though I'm sure there are easier ways to do this if you look through the Date documenation)

Answer 2

Here is an example. If you want it back as a string, you'll have to format it at the end as desired (work with UTC ).

If you put in a date that has the same day number as you're asking of it, it returns the same day, not moving forwards a month.

var date_string = '04092013';
                // MMDDYYYY

function nextNthOfMonth(date_string, n) {
    var date;
    // n to Int, default 1
    n = (+n || 1);
    // date_string to ISO 8601
    date_string = // "yyyy-MM-ddTHH:mm:ssZ"
          date_string.slice(4)
        + '-' + date_string.slice(0, 2)
        + '-' + date_string.slice(2, 4)
        + 'T00:00:00Z';
    // construct date object
    date = new Date(date_string);
    // fix to desired date
    if (n < date.getUTCDate()) { // adjust for month if req.
        date.setUTCMonth(date.getUTCMonth() + 1);
    }
    date.setUTCDate(n);
    return date; // or format as desired
}

nextNthOfMonth(date_string, 1);
// Wed May 01 2013 01:00:00 GMT+0100 (GMT Daylight Time)
nextNthOfMonth(date_string, 15);
// Mon Apr 15 2013 01:00:00 GMT+0100 (GMT Daylight Time)

Answer 3

Try

function getDate() {
    var s = document.getElementById('date').value;
    if(s){
        return new Date(s.substring(4), parseInt(s.substring(2, 4), 10) - 1, s.substring(0, 2))
    }
}

function comingDate(date, day){
    date = new Date(date);
    var cday = date.getDate();
    date.setDate(day);
    if(cday >= day){
        date.setMonth(date.getMonth() + 1)
    }
    return date
}

function f15(){
    var d = getDate();
    var next = comingDate(d, 15);
    console.log(next)
}

function f1(){
    var d = getDate();
    var next = comingDate(d, 1);
    console.log(next)
}

Demo: Fiddle

Answer 4

Since you know the format of your date, split the input into parts:

var dateStr = '04092013'
var month = dateStr.substr(0,2);
var day = dateStr.substr(2,2);
var year = dateStr.substr(4,4);

The construct a new date base on the rule you want to set:

var newDate;
switch(rule)
{
  case 'rule1':
  newDate = new Date(year, month, 1);//first month is 0
  break;
  case 'rule2':
  newDate = new Date(year, month, 15);//first month is 0
  break;
}

• remember to check if the day is greater that 15.