Nearly-Pickled Module

    simple-middleware-manager

    1.0.0 • Public • Published

    Simple middleware manager

    Lightweight and simple yet powerful middleware manager

    CircleCI

    Tool to manage middlewares and/or eventListeners. It works similar to express middlewares with a little more flexibility.

    FAQ

    Why this exists?

    There are not many tools that helps manage middlewares and callbacks and none that have auto mode (see below)

    I found a bug! What should I do?

    Feel free to make a pull request. All contributions are appreciated!

    Usage

    Installing library

    npm i --save simple-middleware-manager

    Registering callbacks

    You can register callback (or eventListeners) using .on method and remove them with .off method

    import createMiddlewareManager from 'simple-middleware-manager';
     
    const manager = createMiddlewareManager();
     
    // adding callbacks/eventListeners
    const listener1 = data => console.log('listener1', data);
    const listener2 = data => console.log('listener2', data);
     
    manager.on('myEvent', listener1);
    manager.on('myEvent', listener2);
     
    manager.trigger('myEvent', 'myData'); // listener1 myData; listener2 myData
     
    // removing callbacks/eventListeners
    manager.off('myEvent', listener2);
     
    manager.trigger('myEvent', 'myData'); // listener1 myData

    Registering callbacks with additional conditions

    You can register eventListeners and add additional conditions that can prevent them from being called

    import createMiddlewareManager from 'simple-middleware-manager';
     
    const manager = createMiddlewareManager();
     
    // adding callbacks/eventListeners
    const listener1 = data => console.log('listener1', data);
    const listener2 = data => console.log('listener2', data);
     
    const condition = (event, data, listener) => {
      if (data === 'foo') {
        listener(data);
      }
    };
     
    manager.on('myEvent', listener1);
    manager.on('myEvent', condition, listener2);
     
    manager.trigger('myEvent', 'myData'); // listener1 myData; listener2 myData
     
    manager.trigger('myEvent', 'myData'); // listener1 myData

    NOTE: adding additional function may seem counter intuitive as the same logic can be just added to the listener. In the case of altering the listener, however, it will make it impossible to remove it later. See the example below:

    Imagine you use middleware-manager internally in another library, that allows you to add conditions:

    yourLibrary.on('eventName', { foo: 'bar' }, listener).

    In that case you can wrap condition in a function and just pass listener unchanged which will allow you to remove it later easily still using simple-middleware-manager mechanism:

    yourLibrary.off('eventName', listener);
    

    Registering middlewares

    • You can add middlewares using .use method, remove them using .unuse or .remove methods.
    • Middlewares will be triggered in the order of registering
    • Each middleware get data as first argument and next() function as second
    • Calling next() function will trigger next middleware
    • You can break middleware pipeline by not calling next
    import createMiddlewareManager from 'simple-middleware-manager';
     
    const manager = createMiddlewareManager();
     
    // adding middlewares
    const middleware1 = (data, next) => {
      console.log('I will be called', data);
      next();
    };
    const middleware2 = (data, next) => {
      console.log('I will be called as well', data);
    }
    const middleware3 = (data, next) => {
      console.log('Will I be called?', data);
      next();
    }
     
    manager.use('myEvent', middleware1);
    manager.use('myEvent', middleware2);
    manager.use('myEvent', middleware3);
     
    manager.trigger('myEvent', 'myData'); // I will be called myData; I will be called as well myData
     
    // removing middlewares
    manager.unuse('myEvent', middleware2);
     
    manager.trigger('myEvent', 'myData'); // I will be called myData; Will I be called? myData

    Using middleware manager in auto mode

    • In auto mode, manager will detect if you passed next as second argument to the middleware
    • If you did, manager will wait for it to be called
    • If you didn't, next() function will be called automatically
    import createMiddlewareManager from 'simple-middleware-manager';
     
    const manager = createMiddlewareManager({ autoMode: true }); // creating manager with autoMode on
     
    // adding middlewares
    const middleware1 = (data) => { // we don't pass next() function so it will be called automatically
      console.log('I will be called', data);
    };
    const middleware2 = (data, next) => {
      console.log('I will be called as well', data);
    }
    const middleware3 = (data, next) => {
      console.log('I will not be called :(', data);
      next();
    }
     
    manager.use('myEvent', middleware1);
    manager.use('myEvent', middleware2);
    manager.use('myEvent', middleware3);
     
    manager.trigger('myEvent', 'myData'); // I will be called myData; I will be called as well myData

    Roadmap

    • Adding conditions function for middlewares

    Install

    npm i simple-middleware-manager

    DownloadsWeekly Downloads

    3

    Version

    1.0.0

    License

    MIT

    Last publish

    Collaborators

    • dyoda