index.js

const byAlpha2 = require("./generated/postal-codes-alpha2.json");
const byAlpha3 = require("./generated/postal-codes-alpha3.json");

let getFormat = require("./formats-web");

module.exports = {
  validate: function(countryCode, postalCode) {
    if (!countryCode) {
      return "Missing country code.";
    }

    if (!postalCode) {
      return "Missing postal code.";
    }

    let countryData = undefined;
    let preparedCountryCode = countryCode.trim().toUpperCase();

    // Is it alpha2 ?
    if (preparedCountryCode.length == 2) {
      countryData = byAlpha2[preparedCountryCode];
    }

    // Is it alpha3 ?
    if (preparedCountryCode.length == 3) {
      countryData = byAlpha3[preparedCountryCode];
    }

    if (!countryData) {
      return "Unknown alpha2/alpha3 country code: " + preparedCountryCode;
    }

    let format = getFormat(countryData.postalCodeFormat);
    if (!format) {
      return (
        'Failed to load postal code format "' +
        countryData.postalCodeFormat +
        '".'
      );
    }

    let preparedPostalCode = postalCode
      .toString()
      .trim()
      .slice(0);
    for (let i = 0; i < format.RedundantCharacters.length; i++) {
      preparedPostalCode = preparedPostalCode.replace(
        new RegExp(format.RedundantCharacters[i], "g"),
        ""
      );
    }

    let expression = format.ValidationRegex;
    if (expression instanceof Array) {
      expression = "^" + expression.join("|") + "$";
    }

    const regexp = new RegExp(expression, "i");
    let result = regexp.exec(preparedPostalCode);

    if (!result) {
      // Invalid postal code
      return (
        "Postal code " +
        preparedPostalCode +
        " is not valid for country " +
        preparedCountryCode
      );
    }

    if (result[0].toLowerCase() != preparedPostalCode.toLowerCase()) {
      // Found "sub" match
      return (
        "Postal code " +
        preparedPostalCode +
        " is not valid for country " +
        preparedCountryCode
      );
    }

    return true;
  }
};