When it comes to working with dates programmers have an easy job if they are working with Javascript - and that's because Javascript has its own date object - an object that enables the computer programmer to:
- create dates
- add and subtract dates
- format dates
The first, and most obvious, date to create, is the current date.
Creating New Dates with Javascript
When a new date object is created with Javascript it is automatically set to the current date and time, for example:
for which the output will be something like:
Other dates can also be set just as easily - and Javascript is very lenient when the programmer comes to this - both of the following will work just as well:
so that:
will produce:
And the Javascript date objects are equally as easy to use when the programmer starts to manipulate the dates.
Adding Dates with Javascript
Javascript date object has a few methods that can be used for the addition of dates, for example getDate and setDate:
Here 31 is added to the current date to give:
However, subtracting one date from another with Javascript is slightly different:
Subtracting One Date from Another with Javascript
The actual process of find the difference between dates is very simple:
It's just the answer that's rather surprising:
This is because the answer is given in milliseconds (and it's worth noting a this point that each date is actually stored as the number of milliseconds since midnight on the 2nd January 1970). Therefore the programmer will need to convert the value into something recognizable, for example:
This code snippet enables the programmer to get the results of 2 days.
Formatting Dates with Javascript
The above examples have shown that it's easy to display the date but that the format is not particularly attractive, however the examples have also shown that it is possible to extract individual part of the day - in addition to the getDate method (which obtains the day of the month) there is also:
- getFullYear - returns the year in 4 figure format
- getMonth - returns the month number (starting with 0=January to 11=December
This means, of course, that a little more processing is required to format the date correctly:
Now the correct month name will be displayed, or the correct month number can be used:
The above code will return 2008/12/22 on the 22nd December 2008.
Summary
Javascript has it's own date object which can be created by using the new method and will, by default, be set to the current date and time. The dates can then be added to (by using the get... and set... methods) and one date can be subtracted from another (for which the result will be in milliseconds). Finally the individual elements of the date of the date by using the get... methods.
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