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component-lifecycle / Monitor

Class: Monitor<P> ​

Monitor class for observing component lifecycle events at the document level.

Example ​

typescript
// Create a monitor for components with prefix "my-component"
const monitor = new Monitor("my-component").start();

// Enable debug tracing for entire application: all component events appear in console.
monitor.setLevel('DEBUG');

// Switch to production mode (silent)
monitor.setLevel('ERROR');

// Check current level
const level = monitor.getLevel(); // "ERROR"

// Stopping monitor
monitor.stop();

Type Parameters ​

P ​

P extends string = "component"

The event prefix to monitor. Defaults to "component".

Constructors ​

Constructor ​

new Monitor<P>(prefix): Monitor<P>

Creates a new Monitor instance for the given event prefix.

Parameters ​

prefix ​

P

The event prefix to monitor (e.g., "component", "my-component")

Returns ​

Monitor<P>

Methods ​

getLevel() ​

getLevel(): LogLevels | undefined

Returns the current logging level.

Returns ​

LogLevels | undefined

The current log level or undefined if the monitor is not started

on() ​

protected on(eventName, handler): this

Adds a single document event listener and tracks it.

This method should be use for automatic cleanup of event listeners in level change or stop.

Parameters ​

eventName ​

string

The base event name (without prefix)

handler ​

(event) => void

The event handler function

Returns ​

this

The Monitor instance for chaining

setLevel() ​

setLevel(level): this

Sets the logging level for this monitor.

Parameters ​

level ​

LogLevels

The log level to set ("DEBUG", "INFO", "WARN", or "ERROR")

Returns ​

this

The Monitor instance for chaining

Remarks ​

  • ERROR: No listeners attached, zero overhead.
  • WARN: Previous level + Listens to transition events (see TransitionEventMap).
  • INFO: Previous level + (no additional events at this level).
  • DEBUG: Previous level + Listens to all lifecycle events (see LifecycleEventMap).

When level changes, all existing listeners are removed and new ones are added based on the new level.

Throws ​

An error if the monitor has not been started

setupDebug() ​

protected setupDebug(): void

Hooks that are called to set up debug level listeners.

Returns ​

void

Remarks ​

This method is intended to be overridden in subclasses calling super.setupDebug() to preserve base functionality.

setupError() ​

protected setupError(): void

Hooks that are called to set up error level listeners.

Returns ​

void

Remarks ​

This method is intended to be overridden in subclasses calling super.setupError() to preserve base functionality.

setupInfo() ​

protected setupInfo(): void

Hooks that are called to set up info level listeners.

Returns ​

void

Remarks ​

This method is intended to be overridden in subclasses calling super.setupInfo() to preserve base functionality.

setupWarn() ​

protected setupWarn(): void

Hooks that are called to set up warn level listeners.

Returns ​

void

Remarks ​

This method is intended to be overridden in subclasses calling super.setupWarn() to preserve base functionality.

start() ​

start(level?): this

Initializes the monitor with the specified log level and attaches the appropriate listeners.

Parameters ​

level? ​

LogLevels = LogLevels.ERROR

The log level to start the monitor with (defaults to ERROR if not specified)

Returns ​

this

The Monitor instance for chaining

Throws ​

An error if the monitor has already been started

stop() ​

stop(): this

Removes all currently active document listeners.

Returns ​

this

The Monitor instance for chaining

Remarks ​

This method is intended to be called when the monitor is no longer needed to clean up resources.

Throws ​

An error if the monitor has not been started