Adding hours to JavaScript Date object?

Question

It amazes me that JavaScript\'s Date object does not implement an add function of any kind.

I simply want a function that can do this:

var now = Date         


        

Answer 1

SPRBRN is correct. In order to account for the beginning/end of the month and year, you need to convert to Epoch and back.

Here's how you do that:

var milliseconds = 0;          //amount of time from current date/time
var sec = 0;                   //(+): future
var min = 0;                   //(-): past
var hours = 2;
var days = 0;

var startDate = new Date();     //start date in local time (we'll use current time as an example)

var time = startDate.getTime(); //convert to milliseconds since epoch

//add time difference
var newTime = time + milliseconds + (1000*sec) + (1000*60*min) + (1000*60*60*hrs) + (1000*60*60*24*days);

var newDate = new Date(newTime); //convert back to date; in this example: 2 hours from right now

or do it in one line (where variable names are the same as above:

var newDate = 
    new Date(startDate.getTime() + millisecond + 
        1000 * (sec + 60 * (min + 60 * (hours + 24 * days))));