CODEWITHSUNDEEP
javascriptdate
108adams
108adams

Reputation: 311

Date() .setDate() inconsistent behaviour

According to

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/setDate

I should expect that setDate() in code 

var now = new Date();
now.setDate(0);

will change now to the last day of the previous month.

It means I should be able to do something like this:

now.setDate(0).setDate(1)

to get the date of the first day of the previous month.

But id doesn't work like that. 

var now = new Date();
console.log(now)
// FF 24: Date {Wed Jul 09 2014 16:35:49 GMT+0100 (IST)}

now.setDate(0);
console.log(now)
// FF 24: Date {Mon Jun 30 2014 16:35:49 GMT+0100 (IST)}

But 

var now = new Date().setDate(0);
console.log(now)
// 1404142784241

Question:

What is difference between 

var now = new Date();
now.setDate(0);

and

var now = new Date().setDate(0);

Upvotes: 0

Views: 192

Answers (1)

Pointy
Pointy

Reputation: 413709

In the second example, you're looking at the return value of the .setDate() function, and not the date itself. The .setDate() function returns the timestamp value corresponding to the updated value of the object. It's like doing this:

var now = new Date();
now.setDate(0);
console.log(now.getTime());

Upvotes: 1

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