Dayjs ES6 module for fullcalendar

dayjs.js

import { createPlugin } from '@fullcalendar/core/index.js';
import { CalendarImpl } from '@fullcalendar/core/internal.js';
import dayjs from 'dayjs/esm/index';
import arraySupport from 'dayjs/esm/plugin/arraySupport';
import customParseFormat from 'dayjs/esm/plugin/customParseFormat';
import duration from 'dayjs/esm/plugin/duration';
import updateLocale from 'dayjs/esm/plugin/updateLocale';
import utc from 'dayjs/esm/plugin/utc';

dayjs.extend(arraySupport);
dayjs.extend(customParseFormat);
dayjs.extend(duration);
dayjs.extend(updateLocale);
dayjs.extend(utc);

function toDayjs(date, calendar) {
	if (!(calendar instanceof CalendarImpl)) {
		throw new Error('must supply a CalendarApi instance');
	}
	let { dateEnv } = calendar.getCurrentData();
	return convertToDayjs(date, dateEnv.timeZone, null, dateEnv.locale.codes[0]);
}

function toDayjsDuration(fcDuration) {
	return dayjs.duration(fcDuration); // dayjs accepts all the props that fc.Duration already has!
}

// Internal Utils
function convertToDayjs(input, timeZone, timeZoneOffset, locale) {
	let mom;
	if (timeZone === 'local') {
		mom = dayjs(input);
	}
	else if (timeZone === 'UTC') {
		mom = dayjs.utc(input);
	}
	else if (dayjs.tz) {
		mom = dayjs.tz(input, timeZone);
	}
	else {
		mom = dayjs.utc(input);
		if (timeZoneOffset != null) {
			mom.utcOffset(timeZoneOffset);
		}
	}
	mom.locale(locale);
	return mom;
}

function formatWithCmdStr(cmdStr, arg) {
	let cmd = parseCmdStr(cmdStr);
	if (arg.end) {
		let startMom = convertToDayjs(arg.start.array, arg.timeZone, arg.start.timeZoneOffset, arg.localeCodes[0]);
		let endMom = convertToDayjs(arg.end.array, arg.timeZone, arg.end.timeZoneOffset, arg.localeCodes[0]);
		return formatRange(cmd, createDayjsFormatFunc(startMom), createDayjsFormatFunc(endMom), arg.defaultSeparator);
	}
	return convertToDayjs(arg.date.array, arg.timeZone, arg.date.timeZoneOffset, arg.localeCodes[0]).format(cmd.whole); // TODO: test for this
}

function createDayjsFormatFunc(mom) {
	return (cmdStr) => (cmdStr ? mom.format(cmdStr) : '' // because calling with blank string results in ISO8601 :(
	);
}

function parseCmdStr(cmdStr) {
	let parts = cmdStr.match(/^(.*?)\{(.*)\}(.*)$/); // TODO: lookbehinds for escape characters
	if (parts) {
		let middle = parseCmdStr(parts[2]);
		return { head: parts[1], middle, tail: parts[3], whole: parts[1] + middle.whole + parts[3] };
	}

	return { head: null, middle: null, tail: null, whole: cmdStr, };
}

function formatRange(cmd, formatStart, formatEnd, separator) {
	if (cmd.middle) {
		let startHead = formatStart(cmd.head);
		let startMiddle = formatRange(cmd.middle, formatStart, formatEnd, separator);
		let startTail = formatStart(cmd.tail);
		let endHead = formatEnd(cmd.head);
		let endMiddle = formatRange(cmd.middle, formatStart, formatEnd, separator);
		let endTail = formatEnd(cmd.tail);
		if (startHead === endHead && startTail === endTail) {
			return startHead +
				(startMiddle === endMiddle ? startMiddle : startMiddle + separator + endMiddle) +
				startTail;
		}
	}

	let startWhole = formatStart(cmd.whole);
	let endWhole = formatEnd(cmd.whole);
	if (startWhole === endWhole) {
		return startWhole;
	}

	return startWhole + separator + endWhole;
}

var index = createPlugin({
	name: 'fullcalendar/dayjs',
	cmdFormatter: formatWithCmdStr,
});

export { index as default, toDayjs, toDayjsDuration };