Find first day of previous month in javascript

Question

Given a date object, how to get its previous month\'s first day in javascript

Answer 1

I like this solution. It might not be the briefest, but it highlights some functions of the setDate() method on Date() objects that not everybody will be familiar with:

function firstDayPreviousMonth(originalDate) {
    var d = new Date(originalDate);
    d.setDate(0); // set to last day of previous month
    d.setDate(1); // set to the first day of that month
    return d;
}

It makes use of the fact that .setDate(0) will change the date to point to the last day of the previous month, while .setDate(1) will change it (further) to point to the first day of that month. It lets the core Javascript libs do the heavy lifting.

You can see a working Plunk here.