function getDecodeCache(exclude) {
  var i, ch, cache = decodeCache[exclude];
  if (cache) { return cache; }

  cache = decodeCache[exclude] = [];

  for (i = 0; i < 128; i++) {
    ch = String.fromCharCode(i);
    cache.push(ch);
  }

  for (i = 0; i < exclude.length; i++) {
    ch = exclude.charCodeAt(i);
    cache[ch] = '%' + ('0' + ch.toString(16).toUpperCase()).slice(-2);
  }

  return cache;
}
LinkifyIt#normalize(match)

Default normalizer (if schema does not define it's own).