JavaScript/TypeScript date formatter


Format any date into a specific date format, this gets rid of the randomness of user's current locale and helps you be more consistent, I highly recommend using the locale date format instead of this for displaying information to the user, but if you are in the backend this should be extremely useful.
You can find a full list of all of the possible combinations Here

Also, this has not been finished yet!

To-Do:

- [X] **`d`** Day of the month, 2 digits with leading zeros	01 to 31
- [X] **`D`** A textual representation of a day, three letters	Mon through Sun
- [ ] **`j`** Day of the month without leading zeros	1 to 31
- [X] **`l`** (lowercase 'L')	A full textual representation of the day of the week	Sunday through Saturday
- [ ] **`N`** ISO-8601 numeric representation of the day of the week	1 (for Monday) through 7 (for Sunday)
- [ ] **`S`** English ordinal suffix for the day of the month, 2 characters	st, nd, rd or th. Works well with j
- [ ] **`w`** Numeric representation of the day of the week	0 (for Sunday) through 6 (for Saturday)
- [ ] **`z`** The day of the year (starting from 0)	0 through 365
- [ ] **`W`** ISO-8601 week number of year, weeks starting on Monday	Example: 42 (the 42nd week in the year)
- [ ] **`F`** A full textual representation of a month, such as January or March	January through December
- [X] **`m`** Numeric representation of a month, with leading zeros	01 through 12
- [ ] **`M`** A short textual representation of a month, three letters	Jan through Dec
- [ ] **`n`** Numeric representation of a month, without leading zeros	1 through 12
- [ ] **`t`** Number of days in the given month	28 through 31
- [ ] **`L`** Whether it's a leap year	1 if it is a leap year, 0 otherwise.
- [ ] **`o`** ISO-8601 week-numbering year. This has the same value as Y, except that if the ISO week number (W) belongs to the previous or next year, that year is used instead.	Examples: 1999 or 2003
- [X] **`Y`** A full numeric representation of a year, 4 digits	Examples: 1999 or 2003
- [ ] **`y`** A two digit representation of a year	Examples: 99 or 03
- [ ] **`a`** Lowercase Ante meridiem and Post meridiem	am or pm
- [X] **`A`** Uppercase Ante meridiem and Post meridiem	AM or PM
- [ ] **`B`** Swatch Internet time	000 through 999
- [ ] **`g`** 12-hour format of an hour without leading zeros	1 through 12
- [ ] **`G`** 24-hour format of an hour without leading zeros	0 through 23
- [ ] **`h`** 12-hour format of an hour with leading zeros	01 through 12
- [X] **`H`** 24-hour format of an hour with leading zeros	00 through 23
- [X] **`i`** Minutes with leading zeros	00 to 59
- [X] **`s`** Seconds with leading zeros	00 through 59
- [ ] **`u`** Microseconds. Note that date() will always generate 000000 since it takes an int parameter, whereas DateTime::format() does support microseconds if DateTime was created with microseconds.	Example: 654321
- [ ] **`v`** Milliseconds. Same note applies as for u.	Example: 654
- [ ] **`e`** Timezone identifier	Examples: UTC, GMT, Atlantic/Azores
- [ ] **`I`** (capital i)	Whether or not the date is in daylight saving time	1 if Daylight Saving Time, 0 otherwise.
- [ ] **`O`** Difference to Greenwich time (GMT) without colon between hours and minutes	Example: +0200
- [ ] **`P`** Difference to Greenwich time (GMT) with colon between hours and minutes	Example: +02:00
- [ ] **`p`** The same as P, but returns Z instead of +00:00	Example: +02:00
- [ ] **`T`** Timezone abbreviation, if known; otherwise the GMT offset.	Examples: EST, MDT, +05
- [ ] **`Z`** Timezone offset in seconds. The offset for timezones west of UTC is always negative, and for those east of UTC is always positive.	-43200 through 50400
- [ ] **`c`** ISO 8601 date	2004-02-12T15:19:21+00:00
- [ ] **`r`** » RFC 2822 formatted date	Example: Thu, 21 Dec 2000 16:01:07 +0200
- [ ] **`U`** Seconds since the Unix Epoch (January 1 1970 00:00:00 GMT)	See also time()

TypeScript

/**
 * Parse a date into a specific string format
 * This function uses the php date formats, as they are extremely simple 
 * @param date The date you would like to input
 * @param format The format you would like the date to be parsed into
 * 
 * @throws Error If anything goes surprisingly wrong
 */
function dateParser(format: string, date: Date = (new Date())): string {
    
    { // d - Day of the month, 2 digits with leading zeros ( 1 - 31 )
        if ( format.includes("d") ) {
            format = format.replace(/d/g, String(date.getDate()).padStart(2, `0`));
        }
    }
    
    { // D - A textual representation of a day, three letters
        if ( format.includes("D") ) {
            // The day of the week
            let dow: string | number = date.getDay();
    
            // Check which string value the day of the week should take
            switch (String(dow)) {
                case `0`: {
                    dow = "Sun";
                    break;
                }
    
                case `1`: {
                    dow = "Mon";
                    break;
                }
    
                case `2`: {
                    dow = "Tue";
                    break;
                }
    
                case `3`: {
                    dow = "Wed";
                    break;
                }
    
                case `4`: {
                    dow = "Thu";
                    break;
                }

                    case `5`: {
                    dow = "Fri";
                    break;
                }
    
                case `6`:{
                    dow = "Sat";
                    break;
                }

                default: throw new Error("Failed the identity of the day");
            }

            // Replace the capital D
            format = format.replace(/D/g, dow);
        }
    }

    { // l ISO-8601 numeric representation of the day of the week
        if ( format.includes("l") ) {
            format = format.replace(/l/g, String(Math.abs(date.getDay() - 10)).padStart(2, `0`));
        }
    }

    { // m 	Numeric representation of a month, with leading zeros
        if ( format.includes("m") ) {
            format = format.replace(/m/g, String(date.getMonth() + 1).padStart(2, `0`));
        }
    }

    { // Y Numeric representation of a month, with leading zeros
        if ( format.includes("Y") ) {
            format = format.replace(/Y/g, String(date.getFullYear()));
        }
    }

    { // H 24-hour format of an hour with leading zeros
        if ( format.includes("H") ) {
            format = format.replace(/H/g, String(date.getHours()).padStart(2, `0`));
        }
    }

    { // i Minutes with leading zeros
        if ( format.includes("i") ) {
            format = format.replace(/i/g, String(date.getMinutes()).padStart(2, `0`));
        }
    }

    { // s Seconds with leading zeros
        if ( format.includes("s") ) {
            format = format.replace(/s/g, String(date.getSeconds()).padStart(2, `0`));
        }
    }

    { // A Uppercase Ante meridiem and Post meridiem
        if ( format.includes("A") ) {
            format = format.replace(/A/g, date.getHours() <= 11 ? "AM" : "PM" );
        }
    }

    // Return the resulting format :)
    return format;
}