import { isFirstDayOfMonth } from "https://deno.land/x/date_fns@v2.0.0-beta.2/index.js";
Examples
// Is 1 September 2014 the first day of a month?
var result = isFirstDayOfMonth(new Date(2014, 8, 1))
//=> true
// Is 1 September 2014 the first day of a month? var result = isFirstDayOfMonth(new Date(2014, 8, 1)) //=> true