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# Basic Logging
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loglevel provides five core logging methods that offer reliable output across all JavaScript environments with proper fallbacks and preserved line numbers.
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## Capabilities
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### trace
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```javascript { .api }
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/**
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 * Output trace message with full stack trace
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 * This will include a full stack trace in supported environments
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 * @param {...any} msg - Any data to log to the console
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 */
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trace(...msg: any[]): void;
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```
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**Usage Examples:**
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```javascript
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import log from 'loglevel';
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log.setLevel('trace');
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log.trace('Entering function processData()');
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log.trace('Processing item:', { id: 123, name: 'example' });
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log.trace('Variable state:', { count: 42, active: true });
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```
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### debug
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```javascript { .api }
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/**
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 * Output debug message to console
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 * Maps to console.debug() if available, otherwise console.log()
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 * @param {...any} msg - Any data to log to the console
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 */
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debug(...msg: any[]): void;
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```
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**Usage Examples:**
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```javascript
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import log from 'loglevel';
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log.setLevel('debug');
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log.debug('Cache miss for key:', 'user_123');
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log.debug('API response:', { status: 200, data: [...] });
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log.debug('Performance metric:', { duration: 245, memory: '12MB' });
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```
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### log
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```javascript { .api }
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/**
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 * Alias for the debug method
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 * Provides familiar console.log-style interface
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 * @param {...any} msg - Any data to log to the console
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 */
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log(...msg: any[]): void;
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```
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**Usage Examples:**
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```javascript
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import logger from 'loglevel';
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logger.setLevel('debug');
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logger.log('This is equivalent to debug()');
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logger.log('User action:', 'clicked_button', { buttonId: 'submit' });
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```
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### info
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```javascript { .api }
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/**
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 * Output informational message
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 * Maps to console.info() if available, otherwise console.log()
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 * @param {...any} msg - Any data to log to the console
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 */
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info(...msg: any[]): void;
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```
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**Usage Examples:**
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```javascript
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import log from 'loglevel';
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log.setLevel('info');
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log.info('Application started successfully');
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log.info('User logged in:', { userId: 456, username: 'john_doe' });
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log.info('Configuration loaded:', { theme: 'dark', locale: 'en-US' });
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```
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### warn
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```javascript { .api }
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/**
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 * Output warning message
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 * Maps to console.warn() if available, otherwise console.log()
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 * @param {...any} msg - Any data to log to the console
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 */
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warn(...msg: any[]): void;
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```
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**Usage Examples:**
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```javascript
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import log from 'loglevel';
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log.setLevel('warn');
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log.warn('Deprecated API usage detected');
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log.warn('Low disk space:', { available: '100MB', threshold: '500MB' });
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log.warn('Rate limit approaching:', { requests: 95, limit: 100 });
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```
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### error
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```javascript { .api }
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/**
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 * Output error message
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 * Maps to console.error() if available, otherwise console.log()
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 * @param {...any} msg - Any data to log to the console
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 */
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error(...msg: any[]): void;
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```
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**Usage Examples:**
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```javascript
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import log from 'loglevel';
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log.setLevel('error');
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log.error('Database connection failed');
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log.error('Validation error:', { field: 'email', message: 'Invalid format' });
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log.error('Unhandled exception:', error.stack);
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```
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## Environment Behavior
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loglevel automatically adapts to different environments:
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- **Modern Browsers**: Uses appropriate console methods (console.trace, console.debug, etc.)
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- **Old Browsers**: Falls back to console.log or no-op if console unavailable
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- **Node.js**: Works with Node's console implementation
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- **IE8/9**: Handles delayed console availability when dev tools are opened
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```javascript
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// Graceful handling - never throws errors
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log.info('This works everywhere');
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// Preserves line numbers and stack traces
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log.debug('Check browser dev tools for accurate source location');
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```