Add One Month to a Date in JavaScript

Question

I have an input field that needs to be incremented by one month using the JavaScript Date object. Below is an example of an effort I have made in incrementing the month. The issue with this seems to be that it will display 0 as January and does not increment the year.

nDate.setDate(nDate.getDate());
inputBox1.value = (nDate.getMonth() + 1) + "/" + (nDate.getDate()) + "/" +  (nDate.getFullYear());

Solution

Use Date.setMonth:

var d = new Date(2000, 0, 1); // January 1, 2000
d.setMonth(d.getMonth() + 1);
console.log(d.getFullYear(), d.getMonth() + 1, d.getDate());

Date.setMonth is range proof i.e. months other than 0...11 are adjusted automatically.

Comments

[leora]

what about december --> january

[Mark Pope]

Hmm, I thought it rolled, but maybe you'll have to explicitly check for that. Or there could be a better way entirely

[leora]

i dont understand your line how its creating a date, it seems like it will create something like 30, 4, 1002

[Mark Pope]

My bad, copy+pasted from one of my apps that does it slightly differently!

[Alnitak]

@leora adding one month to December will cause a year roll. What I don't know is what happens if you roll from the end of a long month into a shorter month.