a utility function `$p()` that creates regular expression patterns from shorthand

shorthand-formatted-regex.js

/**
 * Produces an array of locale-respective formats
 * @template {keyof Intl.DateTimeFormatOptions} K
 * @template {(NonNullable<Intl.DateTimeFormatOptions[K]>)[]} [F=["long", "short"]]
 * @param {K} key - a valid key on the `Intl.DateTimeFormatOptions` object
 * @param {number} quantity - the number of units of the provided option
 * @param {(index: number) => Date} callback - used for creating subsequent dates
 * @param {F} formats - an optional list of formats to generate and key
 * @returns {{ [format in F[number]]: string }[]}
 */
const $f = (key, quantity, callback, formats = ["long", "short"]) =>
  [...Array(quantity)].map((_, i) =>
    formats.reduce((result, format) => ({
      [format]: callback(i).toLocaleString("en", { [key]: format }),
      ...result
    }), {})
  )

/** A reference to the locale-generated named months */
const $M = $f("month", 12, (i) => new Date(0, i))

/** A reference to the locale-generated named weekdays */
const $D = $f("weekday", 7, (i) => new Date(0, 0, i))

/**
 * The shorthand string mapping to regular expression
 * components/patterns (as strings) for use in the interface
 */
const $S = {
  // Currency patterns
  /** Comma-separated values (e.g. "1,000.00") */
  C0_000_00: "(?<!\\.|,|\\d)(?:(?:(?:\\d{1,3},\\d{2})*|\\d{1,2})\\d\\.\\d{2})\\b",
  /** Non comma-separated values (e.g. "1000.00") */
  C0000_00: "\\b\\d+\\.\\d{2}\\b",

  // Readable date pattern components
  /** @see {@link https://en.wikipedia.org/wiki/Date_format_by_country#Table_coding}  */
  /** 4-digit year (e.g. "2020") */
  YYYY: "\\b\\d{4}\\b",
  /** 2-digit year (e.g. 2020 as "20")  */
  YY: "\\b\\d{2}\\b",
  /** The fully named month (e.g. "November") */
  MMMM: `\\b${$M.map(({ long }) => long).join("|")}\\b`,
  /** 3-letter, abbreviated named month (e.g. January as "Jan") */
  MMM: `\\b${$M.map(({ short }) => short).join("|")}\\b`,
  /** 2-digit, zero-leading numeric month (e.g. April as "04") */
  MM: "\\b(?:0[1-9])|(?:1[0-2])\\b",
  /** Non zero-loading numeric month (e.g. May as "5") */
  M: "\\b[1-9]|(?:1[0-2])\\b",
  /** The fully named weekday (e.g. "Wednesday") */
  DDDD: `\\b${$D.map(({ long }) => long).join("|")}\\b`,
  /** 3-letter, abbreviated named weekday (e.g. Friday as "Fri") */
  DDD: `\\b${$D.map(({ short }) => short).join("|")}\\b`,
  /** 2-digit, zero-leading day (e.g. 09 February as "09") */
  DD: "\\b(?:0[1-9])|(?:[1-2][0-9])|(?:3[0-1])\\b",
  /** Non zero-leading day (e.g. 7 December as "7") */
  D: "\\b[1-9]|(?:[1-2][0-9])|(?:3[0-1])\\b",
}

/** An expression that matches the keys for the interface shorthand patterns */
const $P = new RegExp(Object.keys($S).join("|"), "g")

/**
 * Dynamically converts shorthanded patterns from an input string to
 * regular expression
 * @param {string} input - the provided shorthanded string to convert
 * @param {string=} flags - optional RegExp flags to create the expression with
 * @returns - a regular expression object with named groups
 * corresponding to the matched shorthand
 * 
 * @example <caption>Date pattern</caption>
 * // Equivalent pattern:
 * /(?<YYYY>\b\d{4}\b)-(?<MM>\b(?:0[1-9])|(?:1[0-2])\b)-(?<DD>\b(?:0[1-9])|(?:[1-2][0-9])|(?:3[0-1])\b)/
 *
 * "2020-01-01".match($p("YYYY-MM-DD"))
 * 
 * @example <caption>Currency pattern</caption>
 * // Equivalent pattern:
 * /(?<C0_000_00>(?<!\.|,|\d)(?:(?:(?:\d{1,3},\d{2})*|\d{1,2})\d\.\d{2})\b)/
 *
 * "1,749.99".match($p("C0_000_00"))
 */
const $p = (input, flags) =>
  new RegExp(input.replace($P, (match) => `(?<${match}>${$S[match]})`), flags)