def unquote_string(string):
    """Unquote a string with JavaScript rules.  The string has to start with
    string delimiters (``'`` or ``"``.)

    :return: a string
    """
    assert string and string[0] == string[-1] and string[0] in '"\'', \
        'string provided is not properly delimited'
    string = line_join_re.sub('\\1', string[1:-1])
    result = []
    add = result.append
    pos = 0

    while 1:
        # scan for the next escape
        escape_pos = string.find('\\', pos)
        if escape_pos < 0:
            break
        add(string[pos:escape_pos])

        # check which character is escaped
        next_char = string[escape_pos + 1]
        if next_char in escapes:
            add(escapes[next_char])

        # unicode escapes.  trie to consume up to four characters of
        # hexadecimal characters and try to interpret them as unicode
        # character point.  If there is no such character point, put
        # all the consumed characters into the string.
        elif next_char in 'uU':
            escaped = uni_escape_re.match(string, escape_pos + 2)
            if escaped is not None:
                escaped_value = escaped.group()
                if len(escaped_value) == 4:
                    try:
                        add(unichr(int(escaped_value, 16)))
                    except __HOLE__:
                        pass
                    else:
                        pos = escape_pos + 6
                        continue
                add(next_char + escaped_value)
                pos = escaped.end()
                continue
            else:
                add(next_char)

        # bogus escape.  Just remove the backslash.
        else:
            add(next_char)
        pos = escape_pos + 2

    if pos < len(string):
        add(string[pos:])

    return u''.join(result)
dataset/ETHPy150Open mbr/Babel-CLDR/babel/messages/jslexer.py/unquote_string