javascript date difference in days moment code example

Example 1: moment subtract days

var startdate = moment();
startdate = startdate.subtract(1, "days");
startdate = startdate.format("DD-MM-YYYY");

Example 2: moment check days of difference between days

var a = moment([2007, 0, 29]);
var b = moment([2007, 0, 28]);
a.diff(b, 'days')