Skip to main content

Logging and debugging

Reactor uses hierarchical loggers. A module owns a root logger; registered stores inherit a child logger; registered actions inherit from ActionStore. This produces names such as:

Reactor core:Workspace
Reactor core:Actions:Create workspace
Monaco editor:Monaco

Log from modules and stores​

Modules can use their logger directly:

this.logger.info('Todo store ready', { count: this.todos.length });

Stores receive a public logger when registered:

this.logger.debug('Refreshing todos', { currentCount: this.todos.length });
this.logger.warn('Todo metadata is incomplete', todo.id);
this.logger.error('Failed to refresh todos', error);

Choose levels by what the message means:

  • DEBUG for detailed execution and state transitions.
  • INFO for meaningful lifecycle or user-visible operations.
  • WARN for degraded behavior Reactor can recover from.
  • ERROR for failed operations requiring investigation.

Use structured arguments instead of building one large string. Color tokens remain compatible with browser and Node transports:

logger.info('Import complete', Log.green('success'), { imported: count });

Reactor Debug module​

Install @journeyapps/reactor-mod-debug as an application module to add the Reactor debug: Logging panel.

The panel can:

  • search the logger hierarchy;
  • change the global level;
  • override one logger's level;
  • isolate a logger and its children;
  • reset individual overrides back to inheritance.

Configuration is applied immediately and persisted in browser local storage. Resetting preserves the selected global level.

The demo launcher lists Reactor Debug as an optional module and selects it by default.

Pro tip

Name loggers after stores, groups of actions, or subsystems rather than component instances. A developer can then isolate a useful part of the application.

Common pitfall

Do not log credentials, tokens, or private entity payloads. Browser logs and persisted diagnostic choices are user-accessible application state.

Go deeper​

Store lifecycleUser-facing statusDeployment log levels