Converte String UTF8 para Array de Bytes (também desconverte)

string-to-byte-array.js

/**
 * Converts a JS string to a UTF-8 "byte" array.
 * @param {string} str 16-bit unicode string.
 * @return {!Array<number>} UTF-8 byte array.
 */
function stringToUtf8ByteArray(str) {
  // TODO(user): Use native implementations if/when available
  var out = [], p = 0;
  for (var i = 0; i < str.length; i++) {
    var c = str.charCodeAt(i);
    if (c < 128) {
      out[p++] = c;
    } else if (c < 2048) {
      out[p++] = (c >> 6) | 192;
      out[p++] = (c & 63) | 128;
    } else if (
        ((c & 0xFC00) == 0xD800) && (i + 1) < str.length &&
        ((str.charCodeAt(i + 1) & 0xFC00) == 0xDC00)) {
      // Surrogate Pair
      c = 0x10000 + ((c & 0x03FF) << 10) + (str.charCodeAt(++i) & 0x03FF);
      out[p++] = (c >> 18) | 240;
      out[p++] = ((c >> 12) & 63) | 128;
      out[p++] = ((c >> 6) & 63) | 128;
      out[p++] = (c & 63) | 128;
    } else {
      out[p++] = (c >> 12) | 224;
      out[p++] = ((c >> 6) & 63) | 128;
      out[p++] = (c & 63) | 128;
    }
  }
  return out;
};


/**
 * Converts a UTF-8 byte array to JavaScript's 16-bit Unicode.
 * @param {Uint8Array|Array<number>} bytes UTF-8 byte array.
 * @return {string} 16-bit Unicode string.
 */
function utf8ByteArrayToString(bytes) {
  // TODO(user): Use native implementations if/when available
  var out = [], pos = 0, c = 0;
  while (pos < bytes.length) {
    var c1 = bytes[pos++];
    if (c1 < 128) {
      out[c++] = String.fromCharCode(c1);
    } else if (c1 > 191 && c1 < 224) {
      var c2 = bytes[pos++];
      out[c++] = String.fromCharCode((c1 & 31) << 6 | c2 & 63);
    } else if (c1 > 239 && c1 < 365) {
      // Surrogate Pair
      var c2 = bytes[pos++];
      var c3 = bytes[pos++];
      var c4 = bytes[pos++];
      var u = ((c1 & 7) << 18 | (c2 & 63) << 12 | (c3 & 63) << 6 | c4 & 63) -
          0x10000;
      out[c++] = String.fromCharCode(0xD800 + (u >> 10));
      out[c++] = String.fromCharCode(0xDC00 + (u & 1023));
    } else {
      var c2 = bytes[pos++];
      var c3 = bytes[pos++];
      out[c++] =
          String.fromCharCode((c1 & 15) << 12 | (c2 & 63) << 6 | c3 & 63);
    }
  }
  return out.join('');
};