Advanced Usage

Sensitive Data Masking

Protect sensitive information in your logs with built-in masking. Eventum can automatically replace private data with a keyword based on exact field names, partial matches, or regex patterns.

import * as logger from 'eventum';

logger.setConfig({
  prod: {
    output: {
      format: logger.OutputFormat.Json,
      target: logger.OutputTarget.File,
      filePath: './logs/app.log',
      masking: {
        keyword: '***',                              // Replacement text
        exact: ['password', 'token', 'apiKey'],      // Mask these field names
        partial: ['email', 'creditCard'],            // Matches substrings in field names
        regex: ['(?i)bearer\\s+[a-z0-9\\._\\-]+']   // Regex patterns
      }
    }
  }
});

// Sensitive data will be automatically masked
logger.info({
  username: 'alice',
  password: 'secret123',           // Will be masked
  token: 'Bearer abc.def.ghi',     // Will be masked
  email: 'alice@example.com',      // Will be masked (contains 'email')
  userEmail: 'alice@work.com'      // Will be masked (contains 'email')
});

Masking Options

• exact: masks values of fields with an exact name match (e.g. password, token).
• partial: masks values of fields whose names contain any of the given substrings (e.g. user_email, billingEmail).
• regex: masks values matched by custom regex patterns.
• keyword: replacement string (default: [MASKED]).

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Colorized Output

Eventum supports colorized output for better readability during development.

logger.setConfig({
  dev: {
    output: {
      format: logger.OutputFormat.Text,
      target: logger.OutputTarget.Stdout,
      color: true  // Enable colorization
    }
  }
});

Level	Color
trace	Bright Black
debug	Cyan
info	Green
warn	Yellow
error	Red
fatal	Bold Red

TIP

Colors are automatically disabled when color: false or when output is piped to a file.

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Best Practices

Scope-Based Logging

Use the scope field to add context to your logs:

logger.info({ scope: 'AuthService', msg: 'User logged in', userId: '123' });

// In JSON format, scope appears as a top-level field
// In Text format, scope appears in brackets: [AuthService] User logged in

Environment-Specific Configuration

Configure different behavior for dev and prod:

logger.setConfig({
  dev: {
    output: {
      format: logger.OutputFormat.Text,
      target: logger.OutputTarget.Stdout,
      color: true
    }
  },
  prod: {
    output: {
      format: logger.OutputFormat.Json,
      target: logger.OutputTarget.File,
      filePath: './logs/app.log',
      batchEnabled: true,
      batchSize: 100,
      batchIntervalMs: 1000
    }
  }
});