Some of my helper routines commonly used within my Angular projects

general.helper.ts

import { Observable } from 'rxjs'
import moment from 'moment'

export const isEmpty = (obj) => {
    return !obj || Object.keys(obj).length === 0
}

export const isObservable = (obj: any) => {
    return obj instanceof Observable
}


export const decodeString = (str: string): string => Buffer.from(str, 'base64').toString('binary')
export const encodeString = (str: string): string => Buffer.from(str, 'binary').toString('base64')

export function pick<T extends object, U extends keyof T>(obj: T, paths: Array<U>) {
    return paths.reduce((o, k) => {
        o[k] = obj[k]
        return o
    }, Object.create(null))
}

export const groupBy = (items, key) =>
    items.reduce(
        (result, item) => ({
            ...result,
            [item[key]]: [...(result[item[key]] || []), item]
        }),
        {}
    )

export const flattenArrays = (arr) => arr.reduce((a, b) => a.concat(Array.isArray(b) ? flattenArrays(b) : b), [])

export function groupArrayBy(list, keyGetter) {
    const map = new Map()
    list.forEach((item) => {
        const key = keyGetter(item)
        const collection = map.get(key)
        if (!collection) {
            map.set(key, [item])
        } else {
            collection.push(item)
        }
    })
    return map
}

export function addDays(d: Date, days: number): Date {
    return moment(d).utc().add(days, 'day').toDate()
}

export function getMonthDiff(start: Date, end: Date) {
    return moment(start).diff(moment(end), 'month', false)
}

export const uniqueBy = (prop) => (list) => {
    const uniques = {}
    return list.reduce((result, item) => {
        if (uniques[item[prop]]) return result
        uniques[item[prop]] = item
        return [...result, item]
    }, [])
}

export const toCurrency = (n, digits = 2) => {
    return new Intl.NumberFormat('en-GB', {
        minimumFractionDigits: digits,
        style: 'currency',
        currency: 'GBP'
    }).format(n)
}