DateTime Formatting made very very simple

Readme.md

DateUtil

A very simple local-time only date formatting tool that lives in one file and does the minimum for mvp.

How to use

const {format} = require('./dateUtil.js')

let date=Date.now()
let formatStr='www, DD mmmm, YYYY H:I:s.SS'

// Directly format 
console.log( format( formatStr , date ) )

// Register a format
format.quick.register('shorty','YYYY-M-D H:I:S')

// Use the registered Format
console.log( format.quick('shorty',date))

dateUtil.js

const months = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December']
const days = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday']

const parse = (d) => {
    if (!d) return new Date(Date.now())
    if (d instanceof Date) return d
    if (!isNaN(d) && `${d}`.length == 13) return new Date(d)
    return new Date(Date.parse(d))
}

const format = (formatStr, date) => {
    const pad = n => `${n < 10 ? '0' : ''}${n}`
    date = parse(date)

    let day = date.getDate()
    let dow = date.getDay()
    let year = date.getFullYear()
    let month = date.getMonth()
    let hours = date.getHours()
    let minutes = date.getMinutes()
    let seconds = date.getSeconds()
    let ms = date.getMilliseconds()
    let pm = hours > 12 ? true : false

    let out = `${formatStr}`

    out = out.replace(/YYYY/g, year) // 1921
    out = out.replace(/YY/g, `${year}`.slice(-2)) // 21 Year

    out = out.replace(/DD/g, pad(day)) // 08 Day
    out = out.replace(/D/g, day) // 8 Day

    out = out.replace(/AM/g, pm ? 'PM' : 'AM') // AM/PM
    out = out.replace(/Am/g, pm ? 'Pm' : 'Am') // Am/Pm
    out = out.replace(/am/g, pm ? 'pm' : 'am') // am/pm

    out = out.replace(/HH/g, pad(hours)) // 04 14 hours
    out = out.replace(/H/g, hours) // 4 14 hours
    out = out.replace(/hh/g, pad(pm ? hours - 12 : hours)) // 04 02 hours
    out = out.replace(/h/g, pm ? hours - 12 : hours) // 4 2 hours

    out = out.replace(/II/g, pad(minutes)) // 08 minutes
    out = out.replace(/I/g, minutes) // 8 minutes


    out = out.replace(/ss/g, pad(seconds)) // 08 seconds
    out = out.replace(/s/g, seconds) // 8 seconds

    out = out.replace(/SS/g, `${ms < 100 ? '0' : ''}${ms < 10 ? '0' : ''}${ms}`) // 002 ms
    out = out.replace(/S/g, ms) // 2 ms

    out = out.replace(/WWW/g, days[dow].toUpperCase()) // MONDAY
    out = out.replace(/www/g, days[dow]) // Monday
    out = out.replace(/WW/g, days[dow].slice(0, 3).toUpperCase()) //MON
    out = out.replace(/ww/g, days[dow].slice(0, 3)) // Mon
    out = out.replace(/W/g, days[dow].slice(0, 2).toUpperCase()) //MO
    out = out.replace(/w/g, days[dow].slice(0, 2)) // Mo

    out = out.replace(/MMMM/g, months[month].toUpperCase()) // MARCH
    out = out.replace(/mmmm/g, months[month]) // March
    out = out.replace(/MMM/g, months[month].slice(0, 3).toUpperCase()) // MAR
    out = out.replace(/mmm/g, months[month].slice(0, 3)) // Mar
    out = out.replace(/MM/g, pad(month+1)) // 03 Month
    out = out.replace(/M/g, month+1) // 3 Month
    return out
}

format.quick = (formatName, date) => {
    return format(format.quick.registry[formatName], date)
}

format.quick.registry = {}
format.quick.register = (formatName, formatStr) => {
    format.quick.registry[formatName] = formatStr
}


format.quick.register('datetime-local', `YYYY-MM-DDTH:I`)
format.quick.register('iso', `YYYY-MM-DDTH:II:ss.SZ`)

module.exports = { parse, format, months, days }

console.log(format.quick('datetime-local'))
console.log(format.quick('full'))
console.log(format.quick('iso'))
console.log((new Date()).toISOString())