code: function parseExpression() {
  		if ( reader.eof() || (reader.getCurrentToken().type != options.TypeUnescapeExpression && reader.getCurrentToken().type != options.TypeEscapeExpression) ) {
  			return null;
  		}
  
  		if ( reader.getCurrentToken().type == options.TypeEscapeExpression ) {
  			return {type: options.TypeEscapeExpression, src: reader.readToken().text};
  		}else{
  			return {type: options.TypeUnescapeExpression, src: reader.readToken().text};
  		}
  	}
docs: 表达式 { } 或 {= }