Logger API Reference

Comprehensive API reference for the core logger functionality in DoubleTie Logger.

Logger API Reference

This reference documents the core logger functionality in DoubleTie Logger.

`createLogger(options?)`

Creates a configured logger instance with methods for each log level.

Signature:

function createLogger(options?: LoggerOptions | Logger): Logger;

Parameters:

Parameter	Type	Description
`options`	`LoggerOptions \| Logger`	Optional configuration options or an existing logger to extend

LoggerOptions:

Property	Type	Default	Description
`disabled`	`boolean`	`false`	Whether logging is disabled
`level`	`LogLevel`	`'error'`	Minimum log level to publish
`appName`	`string`	`undefined`	Custom application name to display in logs
`log`	`LogHandler`	built-in	Custom log handler function
`formatter`	`string`	`'default'`	Name of the formatter to use
`telemetry`	`TelemetryOptions`	`undefined`	OpenTelemetry configuration

Returns: A logger object with methods for each log level

Example:

import { createLogger } from '@doubletie/logger';
 
const logger = createLogger({
  level: 'info',
  appName: 'payment-service',
  log: (level, message, ...args) => {
    // Custom log handling
    sendToLogService({ level, message, data: args[0] });
  }
});

`logger`

Default logger instance with standard configuration (error level only).

Type: Logger

Example:

import { logger } from '@doubletie/logger';
 
logger.error('Something went wrong');

`LogLevel`

The supported log levels in order of severity (highest to lowest).

Type: 'error' | 'warn' | 'info' | 'success' | 'debug'

Note: The 'success' level is treated as 'info' level when using custom handlers.

`extendLogger(baseLogger, extensions)`

Creates a new logger with additional methods.

Signature:

function extendLogger<Extensions extends LoggerExtensions>(
  baseLogger: Logger,
  extensions: Extensions
): Logger & Extensions;

Parameters:

Parameter	Type	Description
`baseLogger`	`Logger`	The base logger to extend
`extensions`	`Extensions`	Object containing additional methods to add

Returns: A logger with the original methods plus the extensions

Example:

import { createLogger, extendLogger } from '@doubletie/logger';
 
// Create a database logger with custom methods
const dbLogger = extendLogger(
  createLogger({ level: 'debug' }),
  {
    query: (sql: string, params?: any[]) => {
      return dbLogger.debug(`Executing query: ${sql}`, { params });
    },
    connect: (url: string) => {
      return dbLogger.info('Database connected', { url });
    }
  }
);
 
// Use the extended logger
dbLogger.query('SELECT * FROM users WHERE id = ?', [123]);
dbLogger.connect('postgresql://localhost:5432/mydb');

`setLogLevel(level)`

Sets the minimum log level for the default logger.

Signature:

function setLogLevel(level: LogLevel): void;

Parameters:

Parameter	Type	Description
`level`	`LogLevel`	The minimum log level to set

Example:

import { logger, setLogLevel } from '@doubletie/logger';
 
// Enable all logs in development
if (process.env.NODE_ENV !== 'production') {
  setLogLevel('debug');
}

Logger Methods

Each logger instance has the following methods:

`error(message, ...args)`

Log critical issues requiring immediate attention.

Signature:

error(message: string, ...args: unknown[]): void;

Parameters:

Parameter	Type	Description
`message`	`string`	The message to log
`...args`	`unknown[]`	Additional data to include in the log

Example:

logger.error('Failed to connect to database', { 
  host: 'db.example.com',
  port: 5432,
  error: err.message
});

`warn(message, ...args)`

Log potential problems that don't prevent operation.

Signature:

warn(message: string, ...args: unknown[]): void;

Parameters: Same as error method.

Example:

logger.warn('API rate limit approaching', { 
  currentRate: 980,
  limit: 1000,
  resetIn: '30 seconds'
});

`info(message, ...args)`

Log general information about system operation.

Signature:

info(message: string, ...args: unknown[]): void;

Parameters: Same as error method.

Example:

logger.info('User authenticated', { 
  userId: 'user123',
  method: 'oauth',
  provider: 'github'
});

`success(message, ...args)`

Log successful operations.

Signature:

success(message: string, ...args: unknown[]): void;

Parameters: Same as error method.

Example:

logger.success('Payment processed successfully', { 
  amount: 99.99,
  currency: 'USD',
  transactionId: 'tx_12345'
});

`debug(message, ...args)`

Log detailed information useful for debugging.

Signature:

debug(message: string, ...args: unknown[]): void;

Parameters: Same as error method.

Example:

logger.debug('Processing request payload', { 
  headers: req.headers,
  body: req.body,
  params: req.params
});

Logger API Reference