@webilix/jalali-date-time/src/lib/days-in-month.ts

Lightweight library for parsing and formating Jalali date with timezone functionality

import * as JDate from '../script/date';

import { toString } from './string';
import { gregorian } from './gregorian';

export function daysInMonth(): number;
export function daysInMonth(month: string): number;
export function daysInMonth(month?: string): number {
    month = month || toString(new Date(), { format: 'Y-M' });
    if (!JDate.isMonth(month)) throw new TypeError('Invalid Month');

    let daysInMonth: number = 31;
    const jalaliMonth: number = Number(month.substr(5, 2));
    if (jalaliMonth > 6 && jalaliMonth < 12) daysInMonth = 30;
    else if (jalaliMonth === 12) {
        const date: string = gregorian(month + '-30').date + 'T12:00:00';
        const have30Days: boolean = toString(new Date(date)).substr(8, 2) === '30';
        daysInMonth = have30Days ? 30 : 29;
    }

    return daysInMonth;
}