meiosis-router-setup

This is work-in-progress only!

Meiosis is a pattern, not a library. Nevertheless, in response to popular demand and for your convenience, here is a module that helps with setting up a router with Meiosis.

Principles

• Store the route in the application state
• Use the route in the state to determine which page to render, what data to load, etc.
• Clicking on a link, changing the URL in the location bar, etc. changes the route in the state
• Changing the route in the state programmatically synchronizes the URL in the location bar

Coming soon. This is work-in-progress!

This library sets up a router for you and this document explains how to use it. If you are interested in more details of how the router works and how you can implement it yourself, see the Using a Router section of the Meiosis Documentation.

Installation

Using npm:

npm i meiosis-router-setup

Using a script tag:

<script src="https://unpkg.com/meiosis-router-setup"></script>

Using the script tag exposes a MeiosisRouter global, under which the helper functions are provided:

• createRouter
• createMithrilRouter

You will need a third-party router library for parsing URLs. You can use just about any library you like; examples of libraries that work well are:

• feather-route-matcher
• router5
• superouter
• url-mapper

Optionally, if you want to use query strings, add a query string library. The following work out-of-the-box:

• query-string
• qs
• urlon

If you are using Mithril, special support is provided for Mithril Router. Note that Mithril Router already supports query strings, so there is no need for a separate library.

Route Configuration

To configure your routes, use a plain object with the route path templates and a corresponding string page ID. Use the : prefix for path parameters. For example:

const routeConfig = {
  "/": "Home",
  "/login": "Login",
  "/user/:id": "UserProfile"
};

You'll likely want to use string constants instead of hard-coded strings:

const Route = {
  Home: "Home",
  Login: "Login",
  UserProfile: "UserProfile"
};

const routeConfig = {
  "/": Route.Home,
  "/login": Route.Login,
  "/user/:id": Route.UserProfile
};

Hardcoded URL Router Setup

To use feather-route-matcher, you of course need to install it:

npm i feather-route-matcher

Then, use createFeatherRouter to create the router:

import createRouteMatcher from "feather-route-matcher";
import { createFeatherRouter } from "meiosis-router-setup";

const routeConfig = {
  "/": Route.Home,
  "/login": Route.Login,
  "/user/:id": Route.UserProfile
};

const router = createFeatherRouter({ createRouteMatcher, routeConfig });

Use queryString to specify the query string library. For example:

import createRouteMatcher from "feather-route-matcher";
import { createFeatherRouter } from "meiosis-router-setup";
import queryString from "query-string";

const routeConfig = {
  "/": Route.Home,
  "/login": Route.Login,
  "/user/:id": Route.UserProfile
};

const router = createFeatherRouter({ createRouteMatcher, queryString, routeConfig });

Now, router provides the initialRoute property containing the initial route. Use this to initialize your application state. Then, start the router by calling start and providing a function that gets called when the route changes:

router.start(route => update({ route: () => route }));

Normally the function that you provide should call update to update the state with the route, using a patch that corresponds to your Meiosis setup (Mergerino, Function Patches, ...). The example above uses Mergerino.

Next, move on to Using the Router.

Mithril Router Setup

To use Mithril Router, since you are already using Mithril for your application, there is no need to install any other dependency. Moreover, query string support is automatically provided.

Use createMithrilRouter to create the router:

import m from "mithril";
import { createMithrilRouter } from "meiosis-router-setup";

const routeConfig = {
  "/": Route.Home,
  "/login": Route.Login,
  "/user/:id": Route.UserProfile
};

const router = createMithrilRouter({ m, routeConfig });

Then, use m.route and router.createMithrilRoutes to set up your application. Pass your App (root view component), states, update and/or actions (from your Meiosis setup), and an onRouteChange function. The latest state (by calling states()), update, and actions will be passed to your App.

m.route(
  document.getElementById("app"),
  "/",
  router.createMithrilRoutes({ App, states, update, actions,
    onRouteChange: route => update({ route: () => route })
  })
);

The onRouteChange function is called with the route whenever the route changes. Normally the function that you provide should call update to update the state with the route, using a patch that corresponds to your Meiosis setup (Mergerino, Function Patches, ...). The example above uses Mergerino.

Using the Router

The router produces route objects of the form { page: "PageId", params: {...} }, where page is the page ID that corresponds to the route that you specified in your routeConfig ("Home", "Login", "UserProfile", etc.) and params are the path parameters, such as { id: "42" }. If you are using query string support, query string parameters are located under params.queryParams. For example:

{
  page: "PageId",
  params: {
    id: "42",
    queryParams: {
      showAll: "true"
    }
  }
}

With the onRouteChange function that was provided above when setting up the router, update will be called whenever the route changes, and we can access the route under the route property of the application state. Then, we can use state.route.page to determine the current page, state.route.params to get the path parameters, and state.route.params.queryParams for the query string parameters.

To keep the location bar in sync, namely when programmatically changing the route, there are two options.

1. The first option is to use router.locationBarSync:

states.map(state => router.locationBarSync(state.route));

2. The second option, if you are already using effects, is to add router.effect to your array of effects:

const app = {
  ...,
  Effects: update => [
    your.Effect(update),
    ...,
    router.effect
  ]
};

Hash Mode

By default, the router uses hash mode. The hash "#" in the URL is normally used for anchor links, which look like <a href="#example">Example</a>. Setting the URL from /something to /something#example jumps to that location on the same page.

The important thing here is that the browser stays on the same page and does not call the server when the hash changes.

We can take advantage of this by using the hash for our routes. The router listens for hash changes and triggers route updates.

By default, the router uses #! as the hash prefix. Using this prefix makes your pages available for Google search engine indexing and improves your web application's visibility by having your pages appear in Google search results. It is also a convention to indicate that the hash is being used for routing purposes instead of for linking to anchor tags.

If you prefer to use # instead of #! as the hash prefix, specify plainHash: true when creating the router:

const router = createFeatherRouter({ createRouteMatcher, routeConfig, plainHash: true });

const router = createMithrilRouter({ m, routeConfig, plainHash: true });

The following sections assume that you are using the router in hash mode. Following that, we will see how to use the router in history mode.

Adding Links

Next, add links to your application. You can either use hard-coded paths, or the toUrl function.

Using Hard-Coded Paths

With this option, you use hard-coded paths in href:

<a href="#!/">Home</a>
<a href="#!/login">Login</a>
<a href="#!/user/42">User Profile</a>

m("a", { href: "#!/" }, "Home"),
m("a", { href: "#!/login" }, "Login"),
m("a", { href: "#!/user/42" }, "User Profile")

For programmatic routes, use the router.getRoute function and omit the hash-bang ("#!") prefix:

update({ route: () => router.getRoute("/") });
update({ route: () => router.getRoute("/login") });
update({ route: () => router.getRoute("/user/42") });

For convenience, you can write a helper function:

const routeTo = path => ({ route: () => router.getRoute(path) });

update(routeTo("/"));
update(routeTo("/login"));
update(routeTo("/user/42"));

Of course, you also can write helper functions to compute the paths.

Instead of using hard-coded paths, you can use toUrl with page IDs and parameters, as shown below.

Using toUrl

With this option, you provide a page ID and the path and query string parameters to obtain the path:

<a href={router.toUrl(Route.Home)}>Home</a>
<a href={router.toUrl(Route.Login)}>Login</a>
<a href={router.toUrl(Route.UserProfile, { id: 42 })}>User Profile</a>

m("a", { href: router.toUrl(Route.Home) }, "Home"),
m("a", { href: router.toUrl(Route.Login) }, "Login"),
m("a", { href: router.toUrl(Route.UserProfile, { id: 42 }), "User Profile")

For programmatic routes, use the router.getRoute function:

update({ route: () => router.getRoute(Route.Home) });
update({ route: () => router.getRoute(Route.Login) });
update({ route: () => router.getRoute(Route.UserProfile, { id: 42 }) });

For convenience, you can write a helper function:

const routeTo = path => ({ route: () => router.getRoute(path) });

update(routeTo(Route.Home));
update(routeTo(Route.Login));
update(routeTo(Route.UserProfile, { id: 42 }));

History Mode

The router can also operate in history mode instead of hash mode. In history mode, the router uses plain URLs, such as /login and /user/42, instead of URLs with a hash such as #!/login and #!/user/42.

The important thing here is that the browser normally calls the server when the URL changes, and we need to prevent that while navigating within the application. Furthermore, the server must support all possible URLs, since the user could paste a URL in the location bar, or press the browser's Reload button. Server-side support is outside the scope of this documentation.

To use history mode, specify historyMode: true when creating the router:

const router = createFeatherRouter({ createRouteMatcher, routeConfig, historyMode: true });

const router = createMithrilRouter({ m, routeConfig, historyMode: true });

In history mode, we need to prevent links from calling the server. That can be achieved by calling preventDefault on the click event of the link and push the link onto the history. For convenience, the router provides a getLinkHandler function which does that. To use it, create a Link component that you will use for links. The component calls router.toUrl(href) to get the URL, and uses router.getLinkHandler(url) as the onClick event handler.

With React or Preact and using hard-coded paths:

export const Link = ({ href, children, ...props }) => {
  const url = router.toUrl(href);

  return <a href={url} onClick={router.getLinkHandler(url)} {...props}>{children}</a>;
};

<Link href="/login">Login</Link>

Using page IDs:

export const Link = ({ page, params, children, ...props }) => {
  const url = router.toUrl(attrs.page, attrs.params);

  return <a href={url} onClick={router.getLinkHandler(url)} {...props}>{children}</a>;
};

<Link page={Route.UserProfile} params={{ id: 42 }}>User Profile</Link>

With Mithril Router, you can simply use Mithril's m.route.Link:

export const Link = m.route.Link;

m(Link, { href: router.toUrl(Route.UserProfile, { id: 42 }) }, "User Profile"))

Using Services and Effects

Examples

See the examples under the Using a Router section of the Meiosis Documentation Examples.

The realworld example also uses this router pattern.

API

API documentation is here.

---

meiosis-router-setup is developed by foxdonut (@foxdonut00) and is released under the MIT license.