An HTTP-based `Router` in it's simplest form :)

routerException.js

'use strict';

/**
* A very basic `RouterException` class.
**/
export default class RouterException {

  constructor (name, msg) {
    this.name = name;
    this.message = msg;
  }
  
  /** Prettify thrown error **/
  get errorString () {
    return `Exception: ${this.name} ~ message: ${this.message}`;
  }
}

simpleRouter.js

'use strict';

import RouterException from "./routerException"

/**
* An HTTP-based `Router` in it's simplest form :)
**/
class Router {

  constructor () {
    // Protect integrity of internally used router bindings.
    Object.defineProperty(this, '_bindings', {
      value: new Map(),
      writable: true
    });
  }
  
  /** Public API for getting all registered/bound routes. **/
  get routes () {
    return this._bindings.entries();  // List all routes on `this` router instance in insertion order. 
  }
  
  /** Register/update route **/
  bind (url, method, action) {
    switch (true) {
      case Router.httpMethodsWhitelist.indexOf(method) === -1:  // Check HTTP method validity.
        throw new RouterException('InvalidHttpMethodException', 'Specified HTTP method is not recognized');
        
      case !(action instanceof Function): // Is specified action callable?
        throw new RouterException('ActionNotCallableException', 'Could not execute specified route action');
    
      default:
        // Finally, all checks passed, register/update route.
        this._bindings.set(`${method}:${url}`, { action: action });
    }
  }
  
  /** Run registered action against the matched route **/
  runRequest (url, method) {
    let requestedRoute = `${method}:${url}`;  // Build up route URI.
    
    if (!this._bindings.has(requestedRoute)) {  // Check route existence.
      throw new RouterException('ResourceNotFoundException', 'Requested resource is not registered');
    }
    
    // Found `requestedRoute`? Execute associated action.
    return this._bindings.get(requestedRoute).action.call();
  }
  
  static get httpMethodsWhitelist () {
    return ['POST', 'GET', 'PUT', 'DELETE', 'PATCH'];
  }