code: function registerAlias(name, alias) {
    var map = name
    var key
    var list
    var length
    var index
  
    if (alias) {
      map = {}
      map[name] = alias
    }
  
    for (key in map) {
      list = map[key]
      list = typeof list === 'string' ? [list] : list
      length = list.length
      index = -1
  
      while (++index < length) {
        aliases[list[index]] = key
      }
    }
  }
docs: Register more aliases for an already registered language.