displaying the day of the week 3 days before today's date using javascript

Question

I tried this javascript to display the day of the week from 3 days before the html page is accessed. It doesn't work when today is Sunday, Monday or Tuesday. (I think the problem is that the days are numbered 0-6 with no consideration of negative numbers in the line var date)

    var now = new Date();
    var days = new Array(
      'Sunday','Monday','Tuesday','Wednesday','Thursday','Friday','Saturday');
    var months = new Array(
      'January','February','March','April','May',
      'June','July','August','September','October',
      'November','December');
    var date = ((now.getDate()<10) ? "0" : "")+ now.getDate()-3;
    function fourdigits(number) {
      return (number < 1000) ? number + 1900 : number;}
    today =  days[now.getDay() -3] + ", " +
       months[now.getMonth()] + " " +
       date + ", " +
       (fourdigits(now.getYear()));
     document.write(today);

I'd strongly recommend moment.js if you want to do date math or rendering. It's much easier to work with than vanilla js dates — Nick Bailey, Jun 10 '17 at 21:14

RobG · Answer 1 · 2017-06-10T22:53:13.743

There are a number of issues with your code.

<SCRIPT LANGUAGE="JavaScript">

The language attribute for script elements was deprecated in HTML 4 and removed in subsequent versions.

<!--

HTML comment delimiters are tolerated at the start and end of script elements but should not be used. They have been unnecessary for 20 years.

var date = ((now.getDate()<10) ? "0" : "")+ now.getDate()-3;

When the date is 1 to 3, the first part of the expression will return a string like "0" or "". The second part will return a number from -2 to 0, so the result will be "0-2" to "00".

You can do something like:

var date = now.getDate();
date = (date < 10? '0' : '') + date;

Then there is:

today =  days[now.getDay() -3] + ", " +

getDay returns a number representing the day of the week, 0 for Sunday to 6 for Saturday, so from Sunday to Tuesday (day numbers 0–2) you'll be attempting to access a property of days that doesn't exist, which will return undefined.

   (fourdigits(now.getYear()));

getYear always returns the year less 1900. Use getFullYear instead.

See Where can I find documentation on formatting a date in JavaScript? and Add +1 to current date.

You should start by subtracting 3 days from the date, then format the result for output:

var now = new Date();
now.setDate(now.getDate() - 3);
var days = ['Sunday','Monday','Tuesday','Wednesday','Thursday', 'Friday','Saturday'];
var months = ['January','February','March','April','May','June','July',
              'August','September','October','November','December'];
var date = now.getDate();
date = (date < 10? "0" : "") + date;
var today =  days[now.getDay()] + ", " +
             months[now.getMonth()] + " " +
             date + ", " + now.getFullYear();
document.write(today);

This comment may be a repeat: Snippet works fine. Thank you @RobG. How do I run (call ?) it from the site's css file? — Jim Smith, Jun 12 '17 at 16:35
You can't call javascript functions from a CSS file, it's interpreted as *text/css* not *text/javascript*. — RobG, Jun 13 '17 at 00:09
OK, I understand that I cannot call javascript from a CSS file. I don't want the reader of the file where I intend to use this to be able to see and/or copy it by using Source-View. Any suggestions? — Jim Smith, Jun 30 '17 at 17:48
Run it on the server. Anything that goes to the client belongs to the client and the user can do what they want with it. See [*Hiding external JavaScript*](https://stackoverflow.com/questions/2937249/hiding-external-javascript). — RobG, Jun 30 '17 at 22:19

displaying the day of the week 3 days before today's date using javascript

1 Answers1