Convert to UCS2 and from UCS2 in JavaScript

You can use the next function for encoding a simple string to UCS2:

function toUCS2(code) {
  function toPaddedHexString(num, len) {
    const str = num.toString(16).toUpperCase();
    return '0'.repeat(len - str.length) + str;
  }
  const hexers = punycode.ucs2.decode(code);
  let ucs2str = '';
  hexers.forEach((i) => {
    ucs2str += toPaddedHexString(i, 4);
  });
  return ucs2str;
}

Example:

console.log(toUCS2('*123#'));  // '002A0031003200330023'

You can use next function for decoding from UCS2:

function fromUCS2(code) {
  const txt_codes = code.match(/.{1,4}/g);
  let codes = [];
  txt_codes.forEach((i) => {
    codes.push(parseInt(i, 16));
  });
  return punycode.ucs2.encode(codes);
}

Example:

console.log(fromUCS2('002A0031003200330023'));  // '*123#'

You need punycode package for both (use npm install punycode or include as js file).

const punycode = require('punycode');