Copyright	(C) 2016-2026 David M. Johnson
License	BSD3-style (see the file LICENSE)
Maintainer	David M. Johnson <code@dmj.io>
Stability	experimental
Portability	non-portable
Safe Haskell	None
Language	Haskell2010

Miso.Subscription.History

Contents

Subscription
Functions
Types

Description

Overview

Miso.Subscription.History wraps the browser's History API and popstate event, providing both a reactive subscription and imperative navigation helpers.

Subscriptions

uriSub fires whenever the URL changes — through browser back/forward buttons or any of the imperative helpers below:

subs :: [Sub Action]
subs = [ uriSub UrlChanged ]

routerSub is a convenience wrapper that decodes the URI via a Router instance before delivering it as an action:

subs = [ routerSub (RouteChanged . fromRight NotFound) ]

Imperative navigation

These functions push or replace entries on the browser history stack and simultaneously fire a synthetic popstate event so that uriSub and routerSub are notified automatically:

update GoHome     = io_ (pushURI (toURI Home))
update GoProfile  = io_ (pushRoute (User (Capture 42)))
update ReplaceUrl = io_ (replaceURI newUri)
update GoBack     = io_ back
update GoForward  = io_ forward
update (Jump n)   = io_ (go n)

getURI reads the current URL from window.location without subscribing:

update Init = io (GotURI <$> getURI)

uriSub :: (URI -> action) -> Sub action
routerSub :: Router route => (Either RoutingError route -> action) -> Sub action
getURI :: IO URI
pushURI :: URI -> IO ()
pushRoute :: Router route => route -> IO ()
replaceURI :: URI -> IO ()
back :: IO ()
forward :: IO ()
go :: Int -> IO ()
data URI = URI {
- uriPath :: MisoString
- uriFragment :: MisoString
- uriQueryString :: Map MisoString (Maybe MisoString)
}

Subscription

uriSub Source #

Arguments

:: (URI -> action)	Callback fired with the new `URI` on every URL change
-> Sub action

Subscription for URI changes, uses the History API.

This returns a new URI whenever go, back, forward, pushState or replaceState have been called.

routerSub Source #

Arguments

:: Router route
=> (Either RoutingError route -> action)	Callback fired with the decoded route (or `RoutingError`) on every URL change
-> Sub action

Subscription for popstate events, from the History API, mapped to a user-defined Router.

Functions

getURI :: IO URI Source #

Retrieves the current relative URI by inspecting pathname, search and hash.

pushURI Source #

Arguments

:: URI	The URI to push onto the history stack
-> IO ()

Pushes a new URI onto the History stack. Also raises a popstate event.

pushRoute Source #

Arguments

:: Router route
=> route	The route to push onto the history stack (converted to a URI internally)
-> IO ()

Pushes a new Route onto the History stack. Also raises a popstate event.

Converts the Route to a URI internally.

replaceURI Source #

Arguments

:: URI	The URI to replace the current history entry with
-> IO ()

Replaces current URI on stack. Also raises a popstate event.

back :: IO () Source #

Navigates backwards.

forward :: IO () Source #

Navigates forwards.

go Source #

Arguments

:: Int	Number of steps to jump; positive = forward, negative = backward
-> IO ()

Jumps to a specific position in history.

Types

data URI Source #

URI type. See the official specification

Constructors

URI
Fields uriPath :: MisoString Path component, e.g. `"users/42"` uriFragment :: MisoString Fragment identifier (without the leading `#`), e.g. `"section-1"` uriQueryString :: Map MisoString (Maybe MisoString) Query parameters. `Just v` for `?key=v` pairs; `Nothing` for bare flags (`?flag`).