Background information

To support the browser’s back button and bookmarking in a JavaScript application, most applications use the window.location.hash. By changing the hash (via a link or JavaScript), one is able to add to the browser’s history without changing the page.

This provides the basics needed to create history enabled single-page apps. However, route addresses several other needs as well, such as:

• Pretty urls.
• Keeping routes independent of application code.
• Listening to specific parts of the history changing.
• Setup / Teardown of widgets.

How it works

can-route is a map that represents the window.location.hash as an object. For example, if the hash looks like:

#!type=videos&id=5

the data in can-route looks like:

{ type: 'videos', id: 5 }

can-route keeps the state of the hash in-sync with the data contained within it.

data

Underlying can-route is an observable map: can-route.data. Depending on what type of map your application uses, this could be a can-observable-object, a can-define/map/map, an Object, or maybe even a can-simple-map.

can-route is an observable. Once initialized using route.start(), it is going to change, you can respond to those changes. The following example has the my-app component's routeData property return route.data. It responds to changes in routing in componentToShow.

<my-app>
<mock-url>

<script type="module">
import {ObservableObject, StacheElement, route} from "can";
import "//unpkg.com/mock-url@^5";

class PageHome extends StacheElement {
    static view = `
        <h1>Home page</h1>
        <a href="{{ routeUrl(page='other') }}">
            Go to another page
        </a>
    `;
}

customElements.define("page-home", PageHome);

class PageOther extends StacheElement {
    static view = `
        <h1>Other page</h1>
        <a href="{{ routeUrl(page='home') }}">
            Go home
        </a>
    `;
}

customElements.define("page-other", PageOther);

class MyApp extends StacheElement {
    static view = `{{componentToShow}}`;

    static props = {
    routeData: {
      get default() {
        route.data = new ObservableObject();
        route.register("{page}", { page: "home" });
        route.start();
        return route.data;
      }
    },
    get componentToShow() {
      switch(this.routeData.page) {
        case "home":
          return new PageHome();
        case "other":
          return new PageOther();
      }
    }
  };
}

customElements.define("my-app", MyApp);
</script>

route.data defaults to can-observable-object, but route.data can be set to any observable. The following uses [can-define-map]:

import {DefineMap, route} from "can/everything";

const RouteData = DefineMap.extend("RouteData", {
    page: "string"
});

route.data = new RouteData();
route.register( "{page}", { page: "home" } );
route.start();
console.log( route.data.page ) //-> "home"

Understanding how maps work is essential to understanding can-route.

You can listen to changes in a map with on(eventName, handler(ev, args...)) and change can-route’s properties by modifying route.data.

Listening to changes in state

You can listen to changes in the url by listening on the underlying route data. For example, your route data and rule might have a page property:

import {ObservableObject, route} from "can";

route.data = new ObservableObject();
route.register( "{page}", {page: "recipes"} );
route.start();

// You can listen when the url changes from `"#!recipes"` to `"#!settings"` with:

route.data.on( "page", ( ev, newVal, oldVal ) => {
  console.log(oldVal); //-> "recipes"
  console.log(newVal); //-> "settings"
} );

route.data.page = "settings";

Updating can-route

When using an ObservableObject to back can-route, create changes in the route data by modifying it directly:

route.data.page = "images";

Or change multiple properties at once like:

route.data.update( { page: "tasks", id: 5 } );

When you make changes to can-route, they will automatically change the hash.

Encoded /

If the change in your route data includes a /, the / will be encoded into %2F. You will see this result in the URL and location.hash.

<mock-url></mock-url>
<script type="module">
import "//unpkg.com/mock-url@^5.0.0";
import {ObservableObject, route} from "can";

route.data = new ObservableObject( {type: "image/bar"} ); // location.hash -> #!&type=image%2Fbar
route.start();
</script>

Creating a route

Use route.register(url, defaults) to create a routing rule. A rule is a mapping from a url to an object (that is the route’s data). In order to map to specific properties in the url, prepend a colon to the name of the property like:

<mock-url></mock-url>
<script type="module">
import "//unpkg.com/mock-url@^5.0.0";
import {route} from "can";

route.register( "content/{type}" );
route.data.type = "example"; // location.hash -> #!content/example
route.start();
</script>

If no routes are added, or no route is matched, can-route’s data is updated with the deparamed hash.

<mock-url></mock-url>
<script type="module">
import "//unpkg.com/mock-url@^5.0.0";
import {route} from "can";

location.hash = "#!&type=videos";
route.start();

console.log(route.data); //-> {type : "videos"}
</script>

Once routes are added and the hash changes, can-route looks for matching routes and uses them to update can-route’s data.

<mock-url></mock-url>
<script type="module">
import "//unpkg.com/mock-url@^5.0.0";
import {route} from "can";

route.register( "content/{type}" );
location.hash = "#!content/images";
route.start();

console.log( route.data ) //-> {type : "images"}
route.data.type = "songs"; // location.hash -> "#!content/songs"
</script>

Default values can be added to a route, this is the second argument passed into register:

<mock-url></mock-url>
<script type="module">
import "//unpkg.com/mock-url@^5.0.0";
import {route} from "can";

route.register( "content/{type}", {type: "videos"} );
location.hash = "#!content/";

route.start();

console.log( route.data ); //-> {type: "videos"}
// location.hash -> "#!content/"
</script>

Defaults can also be set on the root page of your app. An empty string ("") is treated as the "root" page of the app. If there is no hash, or if using can-route-pushstate someone is at /:

<mock-url></mock-url>
<script type="module">
import "//unpkg.com/mock-url@^5.0.0";
import {route} from "can";

route.register( "", {page: "index"} );
location.hash = "#!";

route.start()

console.log( route.data ); //-> {page : "index"}
// location.hash -> "#!"
</script>

Initializing can-route

After your application has created all of its routes, call start to set can-route’s data to match the current hash:

route.start();

Changing the route

Typically, you don’t set location.hash directly. Instead, you can change properties on can-route like:

route.data.type = "videos";

This will automatically look up the appropriate route and update the hash.

Often, you want to create links. can-stache-route-helpers provides the routeUrl(hashes) helper to make this easy:

<a href="{{ routeUrl(type='videos') }}">Videos</a>

If route.data is an ObservableObject, then route.data.assign( { } ) can be used to overwrite (but not delete) properties and route.data.update( { } ) can be used to overwrite AND delete properties.

If route.data is a can-define/map/map, then route.data.assign( { } ) can be used to overwrite (but not delete) properties and route.data.update( { } ) can be used to overwrite AND delete properties.

Finding the matched route

The matched rule available at route.currentRule and is used to set the window.location.hash. The process can-route uses to find the matched rule is:

1. Find all routes with all of their map properties set
2. If multiple routes are matched, find the route with the highest number of set properties
3. If multiple routes are still matched, use the route that was registered first

Find all routes with all of their map properties set

In order for a route to be matched, all of the map properties it uses must be set. For example, in the following route, page and section must be set in order for this route to be matched:

import {route} from "can";

route.register( "{page}/{section}" );
route.start();

route.data.page = "contact";
route.data.section = "email";

setTimeout(() => {
  const result = route.currentRule();
  console.log( result ); //-> "{page}/{section}"
}, 100);

If a route contains default values, these map properties must also be set to match the default value in order for the route to be matched:

import {route} from "can";

route.register( "{page}", { section: "email" } );
route.start();

route.data.page = "contact";
route.data.section = "email";

setTimeout(() => {
  const result = route.currentRule();
  console.log( result ); //-> "{page}"
}, 100);

Find the route with the highest number of set properties

If multiple routes have all of their properties set, the route with the highest number of set properties will be used:

import {route} from "can";

route.register( "{page}" );
route.register( "{page}/{section}" );
route.start();

route.data.page = "two";
route.data.section = "a";

setTimeout(() => {
  const result = route.currentRule();
  console.log( result ) //-> "{page}/{section}"
}, 100);

Find the route that was registered first

If multiple routes are still matched, the route that was registered first will be matched:

import {route} from "can";

route.register( "", { page: "home" } );
route.register( "{section}" );
route.start();

route.data.page = "home";
route.data.section = "a";

setTimeout(() => {
  const result = route.currentRule();
  console.log(result); //-> ""
}, 100);