API Reference Common

API Reference: Common

Package: @microfrontend/common Version: 1.6.0 Install: npm install @microfrontend/common No peer dependencies

This package is installed in both the shell and every microfrontend. It provides the shared messaging protocol, base classes, and infrastructure.

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Level (enum)

Logging level for controlling console output verbosity.

import { Level } from '@microfrontend/common';

Value	Numeric	Description
OFF	0	No logging
ERROR	1	Errors only
WARNING	2	Errors and warnings
INFO	3	General information (default)
DEBUG	4	Debug-level detail
LOG	5	Maximum verbosity

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MessagingApiBroker

Message broker that translates window.postMessage events into typed handler callbacks. Validates message origins against a whitelist before dispatching.

import { MessagingApiBroker } from '@microfrontend/common';

This class is used internally by MetaRouter and RoutedApp. You typically do not instantiate it directly.

Key behaviors

• Listens for message events on the window
• Validates each message's origin against the allowedOrigins whitelist
• Dispatches typed messages to registered handler callbacks
• Extends Destroyable for lifecycle management

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Destroyable

Base class providing lifecycle management with a destruction guard pattern.

import { Destroyable } from '@microfrontend/common';

Methods

Method	Return	Description
destroy()	void	Marks the object as destroyed. Throws if already destroyed.
isDestroyed()	boolean	Returns true if destroy() has been called
preventUsageUponDestruction()	void	Throws Error if the object has been destroyed

Interface: IDestroyable

import { IDestroyable } from '@microfrontend/common';

Method	Return	Description
destroy()	void	Destroy the object
isDestroyed()	boolean	Check if destroyed

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Message Types

All messages extend MessageBase and are transmitted via window.postMessage between the shell and microfrontends.

MessageBase

Base interface for all messages.

Property	Type	Description
message	string	Message type identifier
source	string	Sender's meta route name (or shell name)

MessageRouted

Sent by a microfrontend to report its current route to the shell.

Property	Type	Description
message	'routed'	—
source	string	Microfrontend's meta route
subRoute	string	Current subroute URL

MessageMetaRouted

Sent by the shell to tell a microfrontend it has been activated.

Property	Type	Description
message	'meta-routed'	—
source	string	Shell name
activated	boolean	Whether the microfrontend is being activated
subRoute	string | undefined	Subroute to navigate to

MessageGoto

Sent by a microfrontend to request navigation to another microfrontend.

Property	Type	Description
message	'goto'	—
source	string	Sender's meta route
metaRoute	string	Target meta route
subRoute	string | undefined	Target subroute

MessageBroadcast

Broadcast message sent between microfrontends (routed through the shell).

Property	Type	Description
message	'broadcast'	—
metadata	MessageBroadcastMetadata	Broadcast metadata
data	object	Payload

MessageBroadcastMetadata

Metadata accompanying a broadcast message.

Property	Type	Description
tag	string	Message tag/type
source	string	Sender's meta route
recipients	string[] | undefined	Target meta routes (all if omitted)
isRecipientVisible	boolean | undefined	Whether the receiving microfrontend is currently visible

MessageSetFrameStyles

Sent by a microfrontend to request iframe style changes.

Property	Type	Description
message	'setFrameStyles'	—
source	string	Microfrontend's meta route
styles	IMap<string>	CSS styles to apply to the iframe

MessageGetCustomFrameConfiguration

Sent as both a request (microfrontend to shell) and a response (shell to microfrontend) for custom iframe configuration data.

Property	Type	Description
message	'getCustomFrameConfiguration'	—
source	string	Sender
configuration	IMap<string>	Configuration key-value pairs

MessageStateChanged

Sent by a microfrontend to report dirty state.

Property	Type	Description
message	'stateChanged'	—
source	string	Microfrontend's meta route
hasState	boolean	Whether the microfrontend has unsaved state
subRoute	string | undefined	Subroute with the state

MessageStateDiscard

Sent by the shell to tell a microfrontend to discard its state.

Property	Type	Description
message	'stateDiscard'	—
source	string	Shell name
metaRoute	string	Target meta route
subRoute	string | undefined	Target subroute

MessageMicrofrontendLoaded

Notification that a microfrontend has finished loading.

Property	Type	Description
message	'microfrontendLoaded'	—
metaRoute	string	Loaded microfrontend's meta route

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IMap<T>

Generic string-keyed dictionary interface used throughout the library.

import { IMap } from '@microfrontend/common';

interface IMap<T> {
  [key: string]: T;
}

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IConsoleFacade

Interface for structured logging.

import { IConsoleFacade } from '@microfrontend/common';

Method	Description
error(message, ...params)	Log an error
warning(message, ...params)	Log a warning
info(message, ...params)	Log information
debug(message, ...params)	Log debug information
log(message, ...params)	Log at max verbosity

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Callback Types

HandleBroadcastNotification

type HandleBroadcastNotification = (metadata: MessageBroadcastMetadata, data: object) => void;

HandleGetCustomFrameConfiguration

type HandleGetCustomFrameConfiguration = (configuration: IMap<string>) => void;