JS gets the first month of the year, the second month to the last month, and the first day to the last day

const start = new Date(new Date().getFullYear(), 1);
// Get January of the current year 1 Japan 
const end = new Date(new Date().getFullYear(), 2);
// Get February of the current year 
end.setTime(end.getTime() - 3600 * 1000 * 24)
// obtain end Last day of the month 
/*  In brackets 1,2  Represents the month you need to get */