// modifiers for skin tones on the Fitzpatrick scale
const modifiers = [
  '\u{1f3fb}', // skin type 1-2
  '\u{1f3fc}', // skin type 3
  '\u{1f3fd}', // skin type 4
  '\u{1f3fe}', // skin type 5
  '\u{1f3ff}', // skin type 6
];

// baby emoji with fitzpatrick skin tone 4
const baby_4 = '👶🏽';

// replaces any skin tone modifiers with the given modifier
// if no modifier is provided, existing modifiers are removed
function replaceModifier (emoji, modifier) {
  let ret = emoji;
  for(let i = 0; i < modifiers.length; i++) {
    ret = `${ret}`.split(modifiers[i]).join(modifier || '');
  }
  return ret;
}

const baby = replaceModifier(baby_4, '');
// 👶

console.log(baby_4);

// change modifiers
for(let i = 0; i < modifiers.length; i++) {
  console.log(replaceModifier(baby_4, modifiers[i]));
}
// 👶🏻
// 👶🏼
// 👶🏽
// 👶🏾
// 👶🏿

// add skin tone modifier to emoji with no skin tone
// supports ZWJ sequences
function addModifier(emoji, baseEmoji, modifier) {
  return emoji.split(baseEmoji).join(baseEmoji + modifier);
}

const peopleHoldingHands = '🧑‍🤝‍🧑';
// 🧑‍🤝‍🧑
const person = '🧑';

// add modifiers
for(let i = 0; i < modifiers.length; i++) {
  console.log(addModifier(peopleHoldingHands, person, modifiers[i]));
}
// 🧑🏻‍🤝‍🧑🏻
// 🧑🏼‍🤝‍🧑🏼
// 🧑🏽‍🤝‍🧑🏽
// 🧑🏾‍🤝‍🧑🏾
// 🧑🏿‍🤝‍🧑🏿