Desktop Logger

The desktop application includes a logging library to display various types of log in the console or in a file.

Four (or five if we count 'mute') log levels are currently implemented:

  • error (1)
  • warn (2)
  • info (3)
  • debug (4)

All messages with an inferior level to the selected one will be displayed. For example, if the selected log level is info, then it will also display warn and error messages.

How to enable logging

Logging can be enabled by running Suite with the command line flag --log-level=LEVEL (replace LEVEL with error, warn, info or debug based on the logging you wish to display). Additional command line flags can be found on the Suite-Desktop page.

API

Exported Types

LogLevel

Any of the following values:

  • mute (0)
  • error (1)
  • warn (2)
  • info (3)
  • debug (4)

Options (all optional)

nametypedefault valuedescription
colorsbooleantrueConsole output has colors
writeToConsolebooleantrueOutput is displayed in the console
writeToDiskbooleanfalseOutput is written to a file
outputFilestring'log-%ts.txt'file name for the output
outputPathstringHome or CWDpath for the output
logFormatstring'%dt - %lvl(%top): %msg'Output format of the log

String formatters

The options outputFile and logFormat can be used with some expressions, prefixed with the percent (%) symbol, to apply certain dynamic elements. It is for example possible to display a timestamp or the current date & time in the listed options above. While some expressions can be used in any strings, some strings have their own expressions.

Global

ExpressionExample outputDescription
%ts1611054460306Timestamp
%dt2021-01-19T11:08:22.244ZDate and time in ISO format (ISO 8601)

logFormat

ExpressionExample outputDescription
%lvlINFOLevel in letters and upper case
%topExampleTopic
%msgExample messageMessage

Constructor

The constructor has the following parameters:

  • level (LogLevel): Selected log level (see LogLevels in Exported Types above)
  • options (Options): Optional parameter containing settings for the logger (see Options in Exported Types above)

Log methods

All log methods have the same signature as they are just wrappers around a private logging method.

The following methods are available:

  • error(topic: string, messages: string | string[]); // level: 1
  • warn(topic: string, messages: string | string[]); // level: 2
  • info(topic: string, messages: string | string[]); // level: 3
  • debug(topic: string, messages: string | string[]); // level: 4

Parameters:

  • topic (string): Message topic
  • messages (string | string[]): Single message or array of messages which will be displayed one by line.

Exit method

The exit() method is used to close the write stream of the log file. If you are not planning to write logs to disk, you won't need to use this method. Otherwise it is highly advised to place this inside exit/crash callbacks.

Example

const logger = new Logger('warn', {
    colors: false, // Turning off colors
    logFormat: '%lvl: %msg', // Level and message only
    writeToDisk: true, // Write to disk
    outputFile: 'log-desktop.txt', // Static file name, will be overwritten if it exists
});

// These messages will be printed with the level provided above
logger.error('example', 'This is an example error message with the topic "example"');
logger.warn('example', 'This is an example warn message with the topic "example"');

// And these won't
logger.info('example', 'This is an example info message with the topic "example"');
logger.debug('example', 'This is an example debug message with the topic "example"');

// Closes the write stream (only needed of writing the log file)
logger.exit();

Q&A

How to format a string?

The library does not have any formatting capabilities as JavaScript already has templating features built-in. Simply use string literals (for example: logger.info('Topic', `My string ${myvar}.`)).

How to output an object?

The library does not include any helper for this as there is already a language feature that does this. Simply use JSON.stringify(myObject).

How can I write the log in JSON format?

You can change the logOutput option to be formatted like JSON. For example: logOutput: '{ "ts": "%ts", "lvl": "%lvl", "topic": "%top", "message": "%msg" },'. In order to display/use it properly, you will have to edit the output a little bit. Wrap all the messages in square brakets ([, ]) and remove the comma (,) from the last message.