I just discovered a neat JavaScript feature that I felt like sharing.

While trying to implement a function that would capture key strokes for certain patterns, like some kind of trigger, I had to compare two dates to get the number of seconds elapsed since the last keystroke.

I first thought to just create a date object, get the seconds and subtract them. But then I would have a problem with long interruptions, which could lead to unpredictable bugs. I could add minutes, but for hour long interruptions, the bug would remain and so on.. Which eventually leads to nearly full date comparison .. yurk.

Then I started missing Python with its awesome ability to compare almost any object types. At this point it hit me, could it be ? .. no ..

I opened Firebug;

>>> a = new Date();
Thu May 21 2009 20:33:14 GMT-0400 (EDT)
>>> b = new Date();
Thu May 21 2009 20:34:15 GMT-0400 (EDT)
>>> a < b
true
>>> a > b
false
>>> a == b
false
>>> a - b
-60596
>>> b - a
60596

I almost cried of joy.

After nearly three years of intensive JavaScript programming it still amaze me. Why I didn't knew about this and why I did not saw this being used anywhere else until now is beyond my understanding.

I'm still not quite sure how it process these though ..

>>> b * a
1.544930730887957e+24
>>> b / a
1.000000048751666

Modulo (%) also works but seems to only do a subtraction.