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SimpleDateFormat for JavaScript

Copyright (c) 2019 Noah Cooper
Dual licensed under MIT and GPL licenses (http://projects.iamnoahcooper.com/license)
Version: 1.4 (26-JAN-2019)

Based on the SimpleDateFormat Java class (https://docs.oracle.com/javase/7/docs/api/java/text/SimpleDateFormat.html)

Overview

With wide support for the Internationalization API, this library is no longer needed in most cases.

While the JavaScript Date object provides developers with methods for working with the individual pieces of a given date, what's missing is a native method for formatting dates as a string following a specified pattern. In Java, SimpleDateFormat provides just that. This project is an attempt to port that functionality to JavaScript in an effort to make it easier to present dates in a human-readable format.

Instantiating simpleDateFormat

The following shows the simpleDateFormat constructor in its most basic form.

var mySimpleDateFormatter = new simpleDateFormat();

The constructor accepts two optional arguments:

  • pattern

    The pattern to use for returned dates. The following subset of pattern letters from SimpleDateFormat are supported:

    y - Year
    M - Month in year
    d - Day in month
    E - Day in week
    a - Am/pm marker
    k(+nn|-nn) - Hour in day (1 - 24)
    h(+nn|-nn) - Hour in am/pm (1 - 12)
    m - Minute in hour

    The pattern letters h and k may be followed by a plus (+) or minus (-) sign and an integer between 1 and 23 to adjust the hour accordingly. This is useful, for example, when working with a Date object in a different timezone.

    As in Java, strings can be quoted using single quotes to avoid interpretation, e.g. "MMMM d, yyyy, 'at' h:mm a". "''" represents a single quote or apostrophe, e.g. "MMMM d, yyyy, 'at' h 'o''clock'".

    If no pattern is provided, the default is "M/d/yy" for the locales en_US and es_US, or "d/M/yy" for en_CA, fr_CA, en_GB, and en_AU.

  • locale

    The locale for returned dates, comprised of an ISO-639 language code and an ISO-3166 country code. The names of months and days will be returned in the locale provided. For example, if the locale is es_US, "d 'de' MMMM 'de' yyyy" will return a date such as "6 de julio de 2012". If locale is fr_CA, "'le' d MMMM yyyy k'h'mm" will return a date such as "le 6 juillet 2012 13h00".

    Currently supported values are "en_US", "es_US", "en_CA", "fr_CA", "en_GB", and "en_AU". The default is "en_US".

The applyPattern Method

The applyPattern method is used to update the pattern which was previously defined.

var mySimpleDateFormatter = new simpleDateFormat();

mySimpleDateFormatter.applyPattern('MMMM d, yyyy');

The method accepts one optional argument:

  • updatedPattern

The updated pattern to apply.

The format Method

The format method is used to format a given date based on the defined pattern. The resulting formatted string is returned.

var mySimpleDateFormatter = new simpleDateFormat('MMMM d, yyyy');

var myDate = new Date('2012', '07', '10');

document.getElementById('myDateContainer').innerHTML = mySimpleDateFormatter.format(myDate);

The method accepts one optional argument:

  • unformattedDate

The date to be formatted. This can be either a Date object, or an ISO-8601 string. If no date is provided, a new Date object is created at the time the method is called.

Examples

Format today's date like "Tuesday, July 10, 2012".

var mySimpleDateFormatter = new simpleDateFormat('EEEE, MMMM d, yyyy');

document.getElementById('myDateContainer').innerHTML = 'Today is ' + mySimpleDateFormatter.format();

Use a pattern which contains an apostrophe.

var mySimpleDateFormatter = new simpleDateFormat('h \'o\'\'clock\'');

document.getElementById('myDateContainer').innerHTML = 'The time is ' + mySimpleDateFormatter.format();

Use the applyPattern method to format a second date using a shorthand for the names of the day and month, like "Tue. Jul 10, 2012".

var mySimpleDateFormatter = new simpleDateFormat('EEEE, MMMM d, yyyy');

document.getElementById('myDateContainer').innerHTML = 'Today is ' + mySimpleDateFormatter.format();

mySimpleDateFormatter.applyPattern('EEE., MMM d, yyyy');

document.getElementById('myDateContainer2').innerHTML = 'Another way to express today\'s date would be ' + mySimpleDateFormatter.format();

Pass an ISO-8601 date/time string to the format method.

var mySimpleDateFormatter = new simpleDateFormat('EEEE');

document.getElementById('myDateContainer').innerHTML = 'Christmas will fall on ' + mySimpleDateFormatter.format('2012-12-25T08:00:30.263-05:00') + ' in 2012';

Adjust the time by 3 hours.

var mySimpleDateFormatter = new simpleDateFormat('h+3:mm');

document.getElementById('myDateContainer').innerHTML = mySimpleDateFormatter.format('2012-07-10T20:00:30.263-05:00');

Express the date in Spanish and French.

var mySpanishSimpleDateFormatter = new simpleDateFormat('d \'de\' MMMM \'de\' yyyy', 'es_US');

document.getElementById('mySpanishDateContainer').innerHTML = mySpanishSimpleDateFormatter.format();

var myFrenchSimpleDateFormatter = new simpleDateFormat('\'le\' d MMMM yyyy k\'h\'mm', 'fr_CA');

document.getElementById('myFrenchDateContainer').innerHTML = myFrenchSimpleDateFormatter.format();