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    1.0.0 • Public • Published

    Multiple Dispatch

    mms for JavaScript and Node written in TypeScript


    > yarn add multiple-dispatch
    > npm install muiltiple-dispatch --save


    import mm from 'multiple-dispatch';
    import homeComponent from './components/home';
    import * as store from './components/store';
    const router = mm({
      name: 'router dispatcher',
      params: [
          name: 'category',
          // This is the default behaviour if you don't have 'isa'
          isa: (dispatchedType: string, override: string) => dispatchedType === override
          name: 'item',
          isa: (dispatchedType: string, override: string) => dispatchedType === override
      throw?: boolean;
    // The 'types' are passed into the override handler, but don't need to be consumed
    router.override(['home', 'main'], (category, item) => homeComponent);
    router.override(['store', 'main'], () => store.main);
    router.override(['store', 'drills'], () => store.drills);
    router.dispatch('store', 'drills'); // Returns store.drills
    router.dispatch('home', 'main'); // Returns homeComponent
    router.dispatch('home', 'invalid'); // Returns null or throws
    function requestHandler(params: { category: string, item: string }) {
      return router.dispatch(params.category, params.item);



    Default export

    import mm from 'multiple-dispatch'
    function create<TDispatch, TReturn>(options: DispatchOptions): Dispatcher<TDispatch, TReturn>
    interface Dispatcher<TReturn, TDispatch> {
      name: string
      override(types: TDispatch[], callback: (...types: TDispatch[]) => TReturn): boolean
      dispatch(...types: TDispatch[]): TReturn | null
    interface DispatchOptions<TDispatch> {
      name: string
      params: Array<{ name: string; isa?: (special: TDispatch, general: TDispatch) => boolean }>
      // Set to true if the desired behaviour is to throw exceptions with invalid usage or ambiguous dispatches.
      throw?: boolean
    interface DispatchHandler<TReturn, TDispatch> {
      types: TDispatch[]
      handler: (...types: TDispatch[]) => TReturn

    isa function

    The isa property in DispatchOptions is for determining if parameter types passed into dispatch has a matching override DisatchHandler.

    During the comparison, the SPECIAL types passed into dispatch(...) are compared against every set of GENERAL types that exist. These are created when override(...) is called.


    // 'home' and 'main' are the GENERAL type during the comparison
    // ['home', 'main'] will be added to the DispatchHandler set.
    // Every type 'set' that exists will be used during comparison to the find the BEST type match.
    router.override(['home', 'main'], handler);
    function (category: string, item: string) {
      // category and item are the SPECIAL type
      return router.dispatch(category, item);


    Dispatcher instance methods. These can throw if throw is set to true in the DispatchOptions.

    function override<TReturn, TDispatch>(types: string[], handler: DispatchHandler<TReturn, TDispatch>): boolean
    function dispatch(...types: string[]): TReturn | null


    npm i multiple-dispatch

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    • seikho