Generate a Country's Flag Emoji given its 2 letter Country Code

flag-emoji.js

// Generate a Country's Flag Emoji given its 2 letter Country Code
// https://emojipedia.org/flags/
function flagEmojiFromCountryCode(code) {
  if (code.length != 2) {
    // Must be ISO 3166-1 alpha-2
    throw new Error(`Country Code "${code}" must be 2 characters`);
  }

  var base = 0x1F1E6 // hex of unicode code point for 🇦, "Regional Indicator Symbol Letter A"
  var a = 'a'.charCodeAt(0) // => 97. Used for calculating unicode offsets from base.

  var offset1 = code.toLowerCase().charCodeAt(0) - a // first character of the country code's offset from a
  var offset2 = code.toLowerCase().charCodeAt(1) - a // second character of the country code's offset from a

  // generate "Regional Indicator Symbol Letter" for each character in the country code
  // https://emojipedia.org/flag-united-states/ 
  var char1 = String.fromCodePoint(base+offset1) // first unicode code point for flag 
  var char2 = String.fromCodePoint(base+offset2) // second unicode code point for flag

  return `${char1}${char2}` // combine unicode code points to make the flag emoji
}

var flag = flagEmojiFromCountryCode('US')
console.log(flag) // => 🇺🇸