function replacer( match, p1 ) {
		var ch = p1[ 1 ];
		var c;

		c = style2ansi( ch );
		if ( c ) {
			reset = RESET;
			len -= 2;
			return c;
		}
		if ( ch === 's' ) {
			len -= 2;
			return RESET;
		}
		if ( ch === '\\' ) {
			len -= 1;
			return '\\\\';
		}
		return '\\\\' + ch;
	}
Callback invoked for each match.

@private
@param {string} match - matched substring
@param {string} p1 - first string found by a parenthesized capture group
@returns {string} replacement string