Javascript Displaying Date

Question

I want to display yesterday's date, and day.

Script for today's date:

<script type="text/javascript">
<!--
  // Array of day names
  var dayNames = new Array("Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday");
  // Array of month Names
  var monthNames = new Array("January","February","March","April","May","June","July","August","September","October","November","December");
  var now = new Date();
  document.write(dayNames[now.getDay()] + ", " + 
  monthNames[now.getMonth()] + " " + 
  now.getDate() + ", " + now.getFullYear());
// -->
</script>

I know that adding a -1 will change the date/year, but it doesn't successfully change the day of the week/month because we have listed the days/months in an array, so there is nothing before Sunday and nothing before January.

How can I display the date from yesterday/however days ago making sure the day and month will change?

mehdi · Accepted Answer · 2014-01-04 22:38:45Z

1

you can try this: see DEMO

dayNames[now.getDay()==0?6:now.getDay()-1]

EDIT:

and for setDate to yesterday : Demo

now.setDate(now.getDate()-1); // set yesterday for now

edited Jan 4, 2014 at 22:38

answered Jan 4, 2014 at 22:06

mehdi

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3 Comments

Trojan Over a year ago

Helpful because it can be dropped in without modifying any existing code, and handles all cases.

Michael Delvege Over a year ago

@mehdi This changes the day/month successfully, but I want it to be able to automatically change the month once the date has reached 0. Not sure if I'm being clear here sorry. This way it's fully automated. So if a visitor views the page on january 1 2014, then it will display that yesterday was december 31 2013.

mehdi Over a year ago

@MichaelDelvege i'v edited my answer, now.setDate(now.getDate()-1); it's set date to yesterday and changing the date and month both.

Pointy · Accepted Answer · 2014-01-04 22:04:55Z

0

You can create a Date instance for yesterday:

var yesterday = new Date();
yesterday.setDate(yesterday.getDate() - 1);

You can then proceed as you're currently doing things. The JavaScript Date code will ensure that the right thing happens with all the other fields. In other words, if "today" is 1 Jan, then "yesterday" will be 31 Dec of the previous year.

answered Jan 4, 2014 at 22:04

Pointy

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Comments

Trojan · Accepted Answer · 2014-01-04 22:07:29Z

0

Yesterday's day of the week: dayNames[(now.getDay() + 6) % 7] (equivalent to -1 + 7)

Last month: monthNames[(now.getMonth() + 11) % 12]

answered Jan 4, 2014 at 22:07

Trojan

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Comments

ngreen · Accepted Answer · 2014-03-21 03:24:22Z

Your best bet is to use a sane date handling library and avoid the horrid 70's-style API that JavaScript provides out-of-the-box. Save your time and sanity and use Moment.js:

// this is a quick way to load, not what I would do for production installs:
eval($.get('http://momentjs.com/downloads/moment.min.js').responseText);
document.write(moment().subtract(1, 'day').format("dddd MMMM D, YYYY"));

Note that this means you can subtract things other than days, like months or years, and it works without you having to remember the math (or DST for that matter):

console.log(moment("2008-02-29").subtract(1, 'year').format("dddd MMMM D, YYYY"))
> Wednesday February 28, 2007
console.log(moment("2008-02-29").add(4, 'years').format("dddd MMMM D, YYYY"))
> Wednesday February 29, 2012
console.log(moment("2008-02-29").add(3, 'years').format("dddd MMMM D, YYYY"))
> Monday February 28, 2011

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