Parse ONLY a time string with DateJS

Question

I'm using the excellent (but large) DateJS library to handle dates and times in my webapp. I just came across something that I'm not sure how to handle.

I want my users to be able to enter Time strings only, without a date, but they should be able to enter it in any manner they please. For instance:

• 5:00 pm
• 17:00
• 5:00pm
• 5:00p
• 5p
• etc.

Using Date.parse(value) converts these strings into a full date, which is exactly what I want. However, it also allows the user to enter any other part of a date string, such as:

• sat 5pm
• 1/1/2010 5pm
• etc.

I'm trying to use DateJS to validate an input field for a time value. Something like:

function validateTime(value) {
    return Date.parse(value) !== null;
}

Is there a way to use DateJS features to solve this? There are other SO questions that provide solutions, but if DateJS has a way to do this, I don't really want to add more custom code to my app to do this.

Answer 1

Shortly after asking my question, I discovered that Date.parseExact() can take an array of format strings. Somehow I'm missed that. I managed to get something working with the following code:

function validateTime(input) {
    return Date.parseExact(input, [
            "H:m",
            "h:mt",
            "h:m t",
            "ht","h t"]) != null ||
        Date.parseExact(input, [
            "h:mtt",
            "h:m tt",
            "htt","h tt"]) != null;
};

Note that some formats don't seem to be able to be included together at the same time, which is why I split them into two separate parseExact() calls. In this case, I couldn't include any string that contained a single t in it with format strings that contained a double tt in it.

Answer 2

The additive approach seems cumbersome. Takes away the beauty of DateJS in my opinion. I needed the same solution and decided to just sneakily append the date in front of my input string before parsing with DateJS:

var parsed = Date.parse(Date.today().toString('M/d/yyyy') + ' ' + this.value);

if (parsed) {
  alert(parsed.toString('h:mm tt'));
}

Now DateJS will not be sniffing around for any of its date-part parsing patterns, as you have already subbed it in.

Hope this helps someone!