How do I format a timestamp in Javascript to display it in graphs? UTC is fine

Question

Basically, I receive raw timestamps and I need to format them into HH:MM:SS format.

Answer 1

Here's a function that provides flexible formatting of a date in UTC. It accepts a format string similar to that of Java's SimpleDateFormat:

function formatDate(date, fmt) {
    function pad(value) {
        return (value.toString().length < 2) ? '0' + value : value;
    }
    return fmt.replace(/%([a-zA-Z])/g, function (_, fmtCode) {
        switch (fmtCode) {
        case 'Y':
            return date.getUTCFullYear();
        case 'M':
            return pad(date.getUTCMonth() + 1);
        case 'd':
            return pad(date.getUTCDate());
        case 'H':
            return pad(date.getUTCHours());
        case 'm':
            return pad(date.getUTCMinutes());
        case 's':
            return pad(date.getUTCSeconds());
        default:
            throw new Error('Unsupported format code: ' + fmtCode);
        }
    });
}

You could use it like this:

formatDate(new Date(timestamp), '%H:%m:%s');