@jsnodor/week-pack/src/index.ts

Utilities to generate arrays made of date objects grouped into 7 items to form a week

(function (global: any) {


    function resetDay(day: Date | string) {
        var date = new Date(day)
        for (var m of ['Hours', 'Minutes', 'Seconds', 'Milliseconds'])
            (date as any)['set' + m](0)
        return date
    }


    /**
     * Generate dates back in time
     * @param startDate The date to start with. This date is not included
     * @param  numweeks The number of weeks to generate
     * @returns A week pack excluding `startDate`
     */
    function prependWeeks(startDate: Date | string | 'today', numWeeks: number = 10) {
        var data: Date[][] = []
        var argDate = startDate == 'today' ? resetDay(new Date) : new Date(startDate)
        var day0 = new Date(argDate.getTime() - (1000 * 60 * 60 * 24)) // Subtract one day
        for (var i = 0; i < numWeeks; i++) {
            var tmp: Date[] = []
            for (var j = 0; j < 7; j++) {
                var dt = new Date(day0.getTime() - ((j + i * 7) * (1000 * 60 * 60 * 24))) // Subtract
                tmp.unshift(dt)
            }
            data.unshift(tmp)
        }
        return data
    }
    /**
     * 
     * @param  startDate Generate dates a head of time
     * @param  numweeks The number of weeks to generate
     * @returns A week pack exluding `startDate`
     */
    function appendWeeks(startDate: Date | string | 'today', numWeeks: number = 10) {
        var data: Date[][] = []
        var argDate = startDate == 'today' ? resetDay(new Date) : new Date(startDate)
        var day0 = new Date(argDate.getTime() + (1000 * 60 * 60 * 24)) // Add one day

        for (var i = 0; i < numWeeks; i++) {
            var tmp: Date[] = []
            for (var j = 0; j < 7; j++) {

                var dt = new Date(day0.getTime() + ((j + i * 7) * (1000 * 60 * 60 * 24))) // Add
                tmp.push(dt)
            }
            data.push(tmp)
        }
        return data
    }


    function generateInitialWeeks(startDate: Date | string | 'today', numWeeks: number = 8) {

        var today = startDate == 'today' ? resetDay(new Date) : new Date(startDate)
        var firstDayOfThisWeek = computeFirstDayOfWeek(today)
        var after = appendWeeks(new Date(firstDayOfThisWeek.getTime() - (1000 * 60 * 60 * 24)), numWeeks) // Subtract one day
        // var after = appendWeeks(dayjs(firstDayOfThisWeek).subtract(1, 'day').toDate())
        var before = prependWeeks(firstDayOfThisWeek, numWeeks)
        var pack = before.concat(after)

        return [firstDayOfThisWeek, today, pack]




        /**
         * Get the first day of the week.
         * @param d The reference date 
         * @returns 
         */
        function computeFirstDayOfWeek(d: Date) {
            d = new Date(d);
            var day = d.getDay(),
                diff = d.getDate() - day + (day == 0 ? -6 : 1); // adjust when day is sunday
            return new Date(d.setDate(diff));
        }
    }

    function isBrowser() {
        var process:any=process||null
        var require:any=require||null
        // Check if the environment is Node.js
        if (typeof process === "object" &&
            typeof require === "function") {
            return false;
        }

        // Check if the environment is a
        // Service worker
        if (typeof importScripts === "function") {
            return false;
        }

        // Check if the environment is a Browser
        if (typeof window === "object") {
            return true;
        }
    }
    const WEEK_PACK = { prependWeeks, appendWeeks, generateInitialWeeks }
    if (isBrowser())
        Object.assign(global, { WEEK_PACK })
    else Object.assign(global, WEEK_PACK)

}(this));