tlvince-react-timeago/lib/formatters/buildFormatter.js.flow

A simple Time-Ago component for ReactJs

// @flow

import type {Formatter, Unit, Suffix} from '../index'

type StringOrFn = string | (value: number, millisDelta:  number) => string
type NumberArray = [
  string,
  string,
  string,
  string,
  string,
  string,
  string,
  string,
  string,
  string
]

export type L10nsStrings = {
  prefixAgo?: ?StringOrFn,
  prefixFromNow?: ?StringOrFn,
  suffixAgo?: ?StringOrFn,
  suffixFromNow?: ?StringOrFn,
  second?: ?StringOrFn,
  seconds?: ?StringOrFn,
  minute?: ?StringOrFn,
  minutes?: ?StringOrFn,
  hour?: ?StringOrFn,
  hours?: ?StringOrFn,
  day?: ?StringOrFn,
  days?: ?StringOrFn,
  week?: ?StringOrFn,
  weeks?: ?StringOrFn,
  month?: ?StringOrFn,
  months?: ?StringOrFn,
  year?: ?StringOrFn,
  years?: ?StringOrFn,
  wordSeparator?: ?string,
  numbers?: NumberArray
}

// If the numbers array is present, format numbers with it,
// otherwise just cast the number to a string and return it
const normalizeNumber = (numbers: ?NumberArray, value: number) =>
  numbers && numbers.length === 10
  ? String(value).split('')
      .map((digit: string) =>
        digit.match(/^[0-9]$/) ? ((numbers: any): NumberArray)[parseInt(digit)] : digit
      ).join('')
  : String(value)

// Take a string or a function that takes number of days and returns a string
// and provide a uniform API to create string parts
const normalizeFn = (value: number, millisDelta: number, numbers: ?NumberArray) => (stringOrFn: StringOrFn) =>
  typeof stringOrFn === 'function'
  ? stringOrFn(value, millisDelta).replace(/%d/g, normalizeNumber(numbers, value))
  : stringOrFn.replace(/%d/g, normalizeNumber(numbers, value))

export default function buildFormatter (strings: L10nsStrings): Formatter {
  return function formatter (value: number, unit: Unit, suffix: Suffix, epochMillis: number) {
    // convert weeks to days if strings don't handle weeks
    const now = Date.now()
    if (unit === 'week' && !strings.week && !strings.weeks) {
      const days = Math.round(Math.abs(epochMillis - now) / (1000 * 60 * 60 * 24))
      value = days
      unit = 'day'
    }

    // create a normalize function for given value
    const normalize = normalizeFn(value, now - epochMillis, strings.numbers)

    // The eventual return value stored in an array so that the wordSeparator can be used
    let dateString: Array<string> = []

    // handle prefixes
    if (suffix === 'ago' && strings.prefixAgo) {
      dateString.push(normalize(strings.prefixAgo))
    }
    if (suffix === 'from now' && strings.prefixFromNow) {
      dateString.push(normalize(strings.prefixFromNow))
    }

    // Handle Main number and unit
    const isPlural = value > 1
    if (isPlural) {
      const stringFn: StringOrFn = strings[unit + 's'] || strings[unit] || '%d ' + unit
      dateString.push(normalize(stringFn))
    } else {
      const stringFn: StringOrFn = strings[unit] || strings[unit + 's'] || '%d ' + unit
      dateString.push(normalize(stringFn))
    }

    // Handle Suffixes
    if (suffix === 'ago' && strings.suffixAgo) {
      dateString.push(normalize(strings.suffixAgo))
    }
    if (suffix === 'from now' && strings.suffixFromNow) {
      dateString.push(normalize(strings.suffixFromNow))
    }

    // join the array into a string and return it
    const wordSeparator = strings.wordSeparator || ' '
    return dateString.join(wordSeparator)
  }
}