API Reference > imodeljs-frontend > Extensions > Extension Extension Class Base Extension class for writing a demand-loaded module. see ExtensionAdmin for a description of how Extensions are loaded. see Extensions Methods Name Description constructor(name: string): Extension Constructor for base Extension class onExecute(_args: string[]): Promise<void> Abstract Method called immediately following the call to onLoad when the Extension is first loaded, and also once for onLoad(_args: string[]): Promise<void> Method called when the Extension is first loaded. resolveResourceUrl(relativeUrl: string): string Returns a fully qualified resource URL which is needed when the extension is loaded from an external server setI18n(defaultNamespace?: string, options?: I18NOptions): void Can be used to set up a localization instance. Deprecated Properties Name Type Description _defaultNs Protected string Subclasses should override this with the default I18N namespace name. i18n Accessor ReadOnly I18N Property that retrieves the localization instance specific to the Extension. name string Defined in core/frontend/src/extension/Extension.ts Line 38 Last Updated: 29 November, 2022