Question

I’m trying to figure out the best way to convert a string containing a time to an integer number of milliseconds. I’m using a suboptimal way using a bunch of preg_match()’s and some array handling, but I was wondering if there was an elegant way.

Here are some example stopwatch times (some wouldn’t actually be seen on a stopwatch but need to be converted anyway):

3:34:05.81

34:05

5 (just 5 seconds)

89 (89 seconds)

76:05 (76 minutes, 5 seconds)

Millseconds will not extend past 2 decimal places. You can give me an example using either PHP or Javascript regex functions.

Thanks!

Answer 1

I wouldn’t bother using a regexp in this case.

Simply explode (split) the strings with ‘:’, and perform a backward analysis – you always have seconds (and maybe milliseconds). Starting with array[lastelement] (seconds) then the previous…

For instance

In PHP

function getMilliseconds($input)
{
  $a = explode(':', $input);
  $n = count($a); // number of array items

  $ms = 0; // milliseconds result

  if ($n > 0)
  {
     $b = explode('.', $a[$n-1]);
     if (count ($b) > 1)
     {
       $m = $b[1];
       while (strlen($m) < 3) $m .= '0'; // ensure we deal with thousands
       $ms += $m;
     }
     $ms += $b[0] * 1000;

     if ($n > 1) // minutes
     {
       $ms += $a[$n-2] * 60 * 1000;

       if ($n > 2) // hours
       {
         $ms += $a[$n-3] * 60 * 60 * 1000;
       }
     }
  }
  return $ms;
}

In JavaScript

(just a PHP to Javascript conversion)

function getMilliseconds(input)
{
  var a = input.split(':');
  var n = a.length; // number of array items

  var ms = 0; // milliseconds result

  if (n > 0)
  {
     var b = a[n-1].split('.');
     if (b.length > 1)
     {
       var m = b[1];
       while (m.length < 3) m += '0'; // ensure we deal with thousands
       ms += m - 0; // ensure we deal with numbers
     }
     ms += b[0] * 1000;

     if (n > 1) // minutes
     {
       ms += a[n-2] * 60 * 1000;

       if (n > 2) // hours
       {
         ms += a[n-3] * 60 * 60 * 1000;
       }
     }
  }
  return ms;
}