I am trying to parse a date of the format January 1, 1900 or February 1, 1900 etc for all of the months.. and then separate the month, day, and year into their own objects.

I have tried using an out-of-the-box regular expression for this but:

1. This particular regex seems overplicated and like it could break easily
2. There has to be an easier regular expression to use knowing that the format will not change (and we will validate the date on the backend)

I don't want to use the DateJS library since it seems like a lot of code to include just to parse one date, so is there an easier way to write a regular expression for this? Is there a different route other than doing regular expressions or DateJS?

For whatever reason, the regular expression does not work for February and as you can see it returns quite a few objects in an array, whereas it would obviously be easier if it just returned 3 objects (month, day, year). Here is the current function I wrote with the regular expression I am using...:

function convertDate(dateString) {
    // must be in the format MMMMMMM DD, YYYY OR MMM DD, YYYY
    // examples: January 1, 2000 or Jan 1, 2000 (notice no period for abbreviating January into Jan)
    var dateRegex = new RegExp('^(?:(((Jan(uary)?|Ma(r(ch)?|y)|Jul(y)?|Aug(ust)?|Oct(ober)?|Dec(ember)?)\\ 31)|((Jan(uary)?|Ma(r(ch)?|y)|Apr(il)?|Ju((ly?)|(ne?))|Aug(ust)?|Oct(ober)?|(Sept|Nov|Dec)(ember)?)\\ (0?[1-9]|([12]\\d)|30))|(Feb(ruary)?\\ (0?[1-9]|1\\d|2[0-8]|(29(?=,\\ ((1[6-9]|[2-9]\\d)(0[48]|[2468][048]|[13579][26])|((16|[2468][048]|[3579][26])00)))))))\\,\\ ((1[6-9]|[2-9]\\d)\\d{2}))');
    var fullDate = dateString.match(dateRegex);
    console.log(fullDate);

    if (fullDate) {
        var month = fullDate[12];
        var day = fullDate[24];
        var year = fullDate[35];

        if (month == 'January' | month == 'Jan') { integerMonth = 1; } 
        else if (month == 'February' | month == 'Feb') { integerMonth = 2; } 
        else if (month == 'March' | month == 'Mar') { integerMonth = 3; } 
        else if (month == 'April' | month == 'Apr') { integerMonth = 4; } 
        else if (month == 'May') { integerMonth = 5; } 
        else if (month == 'June' | month == 'Jun') { integerMonth = 6; } 
        else if (month == 'July' | month == 'Jul') { integerMonth = 7; } 
        else if (month == 'August' | month == 'Aug') { integerMonth = 8; } 
        else if (month == 'September' | month == 'Sep') { integerMonth = 9; } 
        else if (month == 'October' | month == 'Oct') { integerMonth = 10; } 
        else if (month == 'November' | month == 'Nov') { integerMonth = 11; } 
        else if (month == 'December' | month == 'Dec') { integerMonth = 12; } 

        return {month : integerMonth, day : day, year : year}
    } else {
        return false;
    }
}

I am trying to parse a date of the format January 1, 1900 or February 1, 1900 etc for all of the months.. and then separate the month, day, and year into their own objects.

I have tried using an out-of-the-box regular expression for this but:

1. This particular regex seems overplicated and like it could break easily
2. There has to be an easier regular expression to use knowing that the format will not change (and we will validate the date on the backend)

I don't want to use the DateJS library since it seems like a lot of code to include just to parse one date, so is there an easier way to write a regular expression for this? Is there a different route other than doing regular expressions or DateJS?

For whatever reason, the regular expression does not work for February and as you can see it returns quite a few objects in an array, whereas it would obviously be easier if it just returned 3 objects (month, day, year). Here is the current function I wrote with the regular expression I am using...:

function convertDate(dateString) {
    // must be in the format MMMMMMM DD, YYYY OR MMM DD, YYYY
    // examples: January 1, 2000 or Jan 1, 2000 (notice no period for abbreviating January into Jan)
    var dateRegex = new RegExp('^(?:(((Jan(uary)?|Ma(r(ch)?|y)|Jul(y)?|Aug(ust)?|Oct(ober)?|Dec(ember)?)\\ 31)|((Jan(uary)?|Ma(r(ch)?|y)|Apr(il)?|Ju((ly?)|(ne?))|Aug(ust)?|Oct(ober)?|(Sept|Nov|Dec)(ember)?)\\ (0?[1-9]|([12]\\d)|30))|(Feb(ruary)?\\ (0?[1-9]|1\\d|2[0-8]|(29(?=,\\ ((1[6-9]|[2-9]\\d)(0[48]|[2468][048]|[13579][26])|((16|[2468][048]|[3579][26])00)))))))\\,\\ ((1[6-9]|[2-9]\\d)\\d{2}))');
    var fullDate = dateString.match(dateRegex);
    console.log(fullDate);

    if (fullDate) {
        var month = fullDate[12];
        var day = fullDate[24];
        var year = fullDate[35];

        if (month == 'January' | month == 'Jan') { integerMonth = 1; } 
        else if (month == 'February' | month == 'Feb') { integerMonth = 2; } 
        else if (month == 'March' | month == 'Mar') { integerMonth = 3; } 
        else if (month == 'April' | month == 'Apr') { integerMonth = 4; } 
        else if (month == 'May') { integerMonth = 5; } 
        else if (month == 'June' | month == 'Jun') { integerMonth = 6; } 
        else if (month == 'July' | month == 'Jul') { integerMonth = 7; } 
        else if (month == 'August' | month == 'Aug') { integerMonth = 8; } 
        else if (month == 'September' | month == 'Sep') { integerMonth = 9; } 
        else if (month == 'October' | month == 'Oct') { integerMonth = 10; } 
        else if (month == 'November' | month == 'Nov') { integerMonth = 11; } 
        else if (month == 'December' | month == 'Dec') { integerMonth = 12; } 

        return {month : integerMonth, day : day, year : year}
    } else {
        return false;
    }
}

• javascript
• jquery
• regex
• parsing
• date

2 Answers 2

The Javascript Date object can be initialized with a string, and it will parse the format you are using into the correct date:

var d = new Date("January 1, 2000");
if (!isNaN(d.getMonth()) { // check for invalid date
  return {month : d.getMonth()+1, day : d.getDate(), year : d.getFullYear()};
} else {
  return false;
}

As you can see, this function is quite a bit simpler, and should be supported in all modern browsers.

This will work but is not going to be specific to months and years. It just requires 3-9 letters, one or two numbers, one ma and 4 numbers.

/^[a-z]{3,9} [0-9]{1,2}, [0-9]{4}$/i