Mithril

API (v0.1.20)

Core

Routing

m.route

Data

History

m.route

Routing is a system that allows creating Single-Page-Applications (SPA), i.e. applications that can go from a page to another without causing a full browser refresh.

It enables seamless navigability while preserving the ability to bookmark each page individually, and the ability to navigate the application via the browser's history mechanism.

This method overloads four different units of functionality:

m.route(rootElement, defaultRoute, routes) - defines the available URLs in an application, and their respective modules
m.route(path) - redirects to another route
m.route() - returns the currently active route
m.route(element) - an extension to link elements that unobtrusively abstracts away the routing mode

Routing is single-page-application (SPA) friendly, and can be implemented using either location.hash, HTML5 URL rewriting or location.querystring. See m.route.mode for the caveats of each implementation.

Defining routes

Usage

To define a list of routes, you need to specify a host DOM element, a default route and a key-value map of possible routes and respective modules to be rendered.

The example below defines three routes, to be rendered in <body>. home, login and dashboard are modules. We'll see how to define a module in a bit.

m.route(document.body, "/", {
    "/": home,
    "/login": login,
    "/dashboard": dashboard,
});

Routes can take arguments, by prefixing words with a colon :

The example below shows a route that takes an userID parameter

//a sample module
var dashboard = {
    controller: function() {
        this.id = m.route.param("userID");
    },
    view: function(controller) {
        return m("div", controller.id);
    }
}

//define a route
m.route(document.body, "/dashboard/johndoe", {
    "/dashboard/:userID": dashboard
});

//setup routes to start w/ the `#` symbol
m.route.mode = "hash";

This redirects to the URL http://server/#/dashboard/johndoe and yields:

<body>johndoe</body>

Above, dashboard is a module. It contains a controller and a view properties. When the URL matches a route, the respective module's controller is instantiated and passed as a parameter to the view.

In this case, since there's only route, the app redirects to the default route "/dashboard/johndoe".

The string johndoe is bound to the :userID parameter, which can be retrieved programmatically in the controller via m.route.param("userID").

The m.route.mode defines which part of the URL to use for routing.

Variadic routes

We can append an ellipsis (...) to the name of a route argument to allow it to match URL snippets that contain slashes:

m.route(document.body, "/files/pictures/pic1.jpg", {
    "/files/:file...": gallery
});

m.route.param("file") === "pictures/pic1.jpg"

m.route(document.body, "/blog/2014/01/20/articles", {
    "/blog/:date.../articles": articleList
});

m.route.param("date") === "2014/01/20"

Note that Mithril checks for route matches in the order the routes are defined, so you should put variadic routes at the bottom of the list to prevent them from matching other more specific routes.

m.route(document.body, "/blog/archive/2014", {
    "/blog/:date...": module1, //for the default path in the line above, this route matches first!
    "/blog/archive/:year": module2
});

m.route.param("date") === "archive/2014"

//the routes should be flipped around to get `m.route.param("year") == "2014"`

Routes with querystrings

In addition to route parameters, it's possible to pass arbitrary data to m.route.param using the querystring

m.route("/grid?sortby=date&dir=desc")

var sortBy = m.route.param("sortby") // "date"
var dir = m.route.param("dir") // "desc"

Running clean up code on route change

If a module's controller implements an instance method called onunload, this method will be called when a route changes.

var home = {};
home.controller = function() {
    this.onunload = function() {
        console.log("unloading home module");
    };
};

var dashboard = {};
dashboard.controller = function() {};
dashboard.view = function() {};

//go to the default route (home)
m.route(document.body, "/", {
    "/": home,
    "/dashboard": dashboard,
});

//re-route to dashboard
m.route("/dashboard"); // logs "unloading home"

This mechanism is useful to clear timers and unsubscribe event handlers. If you have a hierarchy of components, you can recursively call unload on all the components in the tree or use a pubsub library to unload specific components on demand.

Signature

How to read signatures

void route(DOMElement rootElement, String defaultRoute, Object<Module> routes) { String mode, String param(String key) }

where:
    Module :: Object { void controller(), void view(Object controllerInstance) }

DOMElement root

A DOM element which will contain the view's template.
String defaultRoute

The route to redirect to if the current URL does not match any of the defined routes
Object routes

A key-value map of possible routes and their respective modules. Keys are expected to be absolute pathnames, but can include dynamic parameters. Dynamic parameters are words preceded by a colon :

{'/path/to/page/': pageModule} - a route with a basic pathname

{'/path/to/page/:id': pageModule} - a route with a pathname that contains a dynamic parameter called id. This route would be selected if the URL was /path/to/page/1, /path/to/page/test, etc

{'/user/:userId/book/:bookId': userBookModule} - a route with a pathname that contains two parameters

Dynamic parameters are wild cards that allow selecting a module based on a URL pattern. The values that replace the dynamic parameters in a URL are available via m.route.param()

Note that the URL component used to resolve routes is dependent on m.route.mode. By default, the querystring is considered the URL component to test against the routes collection

If the current page URL matches a route, its respective module is activated. See m.module for information on modules.
m.route.mode

String mode

The m.route.mode property defines which URL portion is used to implement the routing mechanism. Its value can be set to either "search", "hash" or "pathname". Default value is "search". Note that if you're changing this configuration value, you should change it before calling m.route.
- search mode uses the querystring (i.e. ?). This allows named anchors (i.e. <a href="#top">Back to top</a>, <a name="top"></a>) to work on the page, but routing changes causes page refreshes in IE8, due to its lack of support for history.pushState.
  
  Example URL: http://server/?/path/to/page
- hash mode uses the hash (i.e. #). It's the only mode in which routing changes do not cause page refreshes in any browser. However, this mode does not support named anchors.
  
  Example URL: http://server/#/path/to/page
- pathname mode allows routing URLs that contains no special characters, however this mode requires server-side setup in order to support bookmarking and page refreshes. It also causes page refreshes in IE8.
  
  Example URL: http://server/path/to/page
  
  The simplest server-side setup possible to support pathname mode is to serve the same content regardless of what URL is requested. In Apache, this URL rewriting can be achieved using ModRewrite.
m.route.param

String param(String key)

Route parameters are dynamic values that can be extracted from the URL based on the signature of the currently active route.

A route without parameters looks like this:

"/path/to/page/"

A route with parameters might look like this:

"/path/to/page/:id" - here, id is the name of the route parameter

If the currently active route is /dashboard/:userID and the current URL is /dashboard/johndoe, then calling m.route.param("userID") returns "johndoe"

Querystring parameters in a route are also available in this collection automatically.

"/grid?sortby=date" - here, m.route.param("sortby") returns "date"
- String key
  
  The name of a route parameter
- returns String value
  
  The value that maps to the parameter specified by key

Redirecting

Usage

You can programmatically redirect to another page. Given the example in the "Defining Routes" section:

m.route("/dashboard/marysue");

redirects to http://server/#/dashboard/marysue

Signature

How to read signatures

void route(String path [, any params])

String path

The route to redirect to. Note that to redirect to a different page outside of the scope of Mithril's routing, you should use window.location
any params

Parameters to pass as a querystring

Reading the currently active route

Usage

Mithril updates the native location object after rendering in order to allow the browser's history.pushState API to correctly show descriptive history entries (e.g. for Chrome's Ctrl+H page).

In order to retrieve the currently active route in a controller, you can use m.route(). This returns the portion of the URL determined by m.route.mode (minus the ? or # symbols for the search and hash modes, respectively).

//if the location bar is "http://example.com/?/foo/bar"
//and m.route.mode is `search`
//then `currentRoute == "/foo/bar"`
var currentRoute = m.route();

Signature

How to read signatures

String route()

returns String route

returns the currently active route

Mode abstraction

Usage

This method is meant to be used with a virtual element's config attribute. For example:

//Note that the '#' is not required in `href`, thanks to the `config` setting.
m("a[href='/dashboard/alicesmith']", {config: m.route});

This makes the href behave correctly regardless of which m.route.mode is selected. It's a good practice to always use the idiom above, instead of hardcoding ? or # in the href attribute.

See m() for more information on virtual elements.

Signature

How to read signatures

void route(DOMElement element, Boolean isInitialized)

DOMElement element

an anchor element <a> with an href attribute that points to a route
Boolean isInitialized

the method does not run if this flag is set to true. This is to make the method compatible with virtual DOM elements' config attribute (see m())