6 declarations
(value: string | undefined): LogLevel | undefined import {log_level_parse} from '@fuzdev/fuz_util/log.js'; Parses and validates a log level string.
valuestring | undefinedLogLevel | undefined the validated log level, or undefined if value is undefined
Error - if `value` is provided but invalid(level: LogLevel): number import {log_level_to_number} from '@fuzdev/fuz_util/log.js'; Converts a log level to its numeric value for comparison. Higher numbers indicate more verbose logging.
levelnumber numeric value (0-4)
LogConsole import type {LogConsole} from '@fuzdev/fuz_util/log.js'; Console interface subset used by Logger for output. Allows custom console implementations for testing.
Pick<typeof console, 'error' | 'warn' | 'log'>import {Logger} from '@fuzdev/fuz_util/log.js'; Simple, flexible logger with support for child loggers and automatic context.
Features:
// Basic logger
const log = new Logger('app');
log.info('starting'); // [app] ➤ starting
// Child logger
const db_log = log.child('db');
db_log.info('connected'); // [app:db] ➤ connected
// Custom configuration
const verbose_log = new Logger('debug', { level: 'debug', colors: true });label?type string
parent?type Logger
constructorCreates a new Logger instance.
type new (label?: string | undefined, options?: LoggerOptions): Logger
label?optional label for this logger. Can be undefined for no label, or an
empty string '' which is functionally equivalent (both produce no brackets in output).
Note: Empty strings are only allowed for root loggers - child loggers cannot have empty labels.
string | undefinedoptionsoptional configuration for level, colors, and console
{}clear_level_overrideClears the level override for this logger, restoring inheritance from parent. After calling this, the logger will dynamically inherit the level from its parent (or use the default level if it has no parent).
type (): void
voidclear_colors_overrideClears the colors override for this logger, restoring inheritance from parent. After calling this, the logger will dynamically inherit colors from its parent (or use the default colors behavior if it has no parent).
type (): void
voidclear_console_overrideClears the console override for this logger, restoring inheritance from parent. After calling this, the logger will dynamically inherit the console from its parent (or use the global console if it has no parent).
type (): void
voidchildCreates a child logger with automatic label concatenation. Children inherit parent configuration unless overridden.
type (label: string, options?: LoggerOptions): Logger
labelchild label (will be concatenated with parent label using :)
Cannot be an empty string - empty labels would result in confusing output like parent:
with a trailing colon. Use undefined or '' only for root loggers.
stringoptionsoptional configuration overrides
{}new Logger instance with concatenated label
const app_log = new Logger('app');
const db_log = app_log.child('db'); // label: 'app:db'
const query_log = db_log.child('query'); // label: 'app:db:query'throws
Error - if label is an empty stringerrorLogs an error message with 🞩error🞩 prefix.
Only outputs if current level is error or higher.
type (...args: unknown[]): void
argsunknown[]voidwarnLogs a warning message with ⚑warn⚑ prefix.
Only outputs if current level is warn or higher.
type (...args: unknown[]): void
argsunknown[]voidinfoLogs an informational message.
Unlike error/warn/debug, info has no character prefix - only the label is shown.
This keeps standard output clean since info is the default log level.
Only outputs if current level is info or higher.
type (...args: unknown[]): void
argsunknown[]voiddebugLogs a debug message with ┆debug┆ prefix.
Only outputs if current level is debug.
type (...args: unknown[]): void
argsunknown[]voidrawLogs raw output without any prefix, formatting, or level filtering. Bypasses the logger's level checking, prefix formatting, and color application entirely.
Note: This method ignores the configured log level - it always outputs regardless of
whether the logger is set to 'off' or any other level.
type (...args: unknown[]): void
argsunknown[]voidlevelDynamic getter for level - checks override, then parent, then default.
type LogLevel
colorsDynamic getter for colors - checks override, then parent, then environment variables.
Colors are disabled if either the NO_COLOR or CLAUDECODE environment variable is set.
The CLAUDECODE check disables colors in Claude Code environments where ANSI color codes
may not render correctly in the output.
type boolean
consoleDynamic getter for console - checks override, then parent, then global console.
type LogConsole
rootGets the root logger by walking up the parent chain. Useful for setting global configuration that affects all child loggers.
type Logger
LoggerOptions import type {LoggerOptions} from '@fuzdev/fuz_util/log.js'; level?Log level for this logger instance. Inherits from parent or defaults to 'info'.
type LogLevel
console?Console interface for output. Inherits from parent or defaults to global console. Useful for testing.
type LogConsole
colors?Whether to use colors in output. Inherits from parent or defaults to enabled (unless NO_COLOR env var is set).
type boolean
LogLevel import type {LogLevel} from '@fuzdev/fuz_util/log.js'; Log level hierarchy from least to most verbose.
'off': No logging'error': Only errors'warn': Errors and warnings'info': Errors, warnings, and info (default)'debug': All messages including debug