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Tiny, state-based, advanced router for SvelteJS.

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509 kB




  • add support for svelte 4



Tiny, state-based, advanced router for SvelteJS.

NPM version NPM downloads

A completely different approach of routing. State-based router suggests that routing is just another global state and History API changes are just an optional side-effects of this state.

💡 Features

  • Zero-config!
  • Just another global state. Ultimate freedom how to apply this state to your app!
  • Juggling of different parts of URL (path/query/hash) effective and granularly.
  • Automatic parsing of the query params, optional parsing path params.
  • Helpers to work with navigation, links, and even html forms.


📦 Install

npm i svelte-pathfinder --save-dev
yarn add svelte-pathfinder

CDN: UNPKG | jsDelivr (available as window.Pathfinder)

<script src=""></script>

<!-- OR in modern browsers -->

<script type="module" src=""></script>

📌 URL schema




path - represents path segments of the URL as an array.

path: Writable<[]>

query - represents query params of the URL as an object.

query: Writable<{}>

fragment - represents fragment (hash) string of URL.

fragment: Writable<string>

state - represents state object associated with the new history entry created by pushState().

state: Writable<{}>

url - represents full URL string.

url: Readable<string>

pattern - function to match path patterns and return read-only params object or null.

pattern: Readable<<T extends {}>(pattern?: string | RegExp, options?: ParseParamsOptions) => T | null>

paramable - constructor of custom params stores to parse path patterns and manipulate path parameters.

paramable: <T extends {}>(pattern?: string, options?: ParseParamsOptions): Writable<T>;


goto - perform navigation to the next router state by URL.

goto(url: string | URL, state?: {});

back - perform navigation to the previous router state.

back(url?: string | URL)

redirect - update current url without new history record.

redirect(url: string | URL, state?: {})

click - handle click event from the link and perform navigation to its targets.

click(event: MouseEvent)

submit - handle submit event from the GET-form and perform navigation using its inputs.

submit(event: SubmitEvent)


  • prefs - preferences object
    • sideEffect - manually disable/enable History API usage (changing URL) (default: auto).
    • hashbang - manually activate hashbang-routing.
    • base - set base path if web app is located within a nested basepath.
    • convertTypes - disable converting types when parsing query/path parameters (default: true).
    • nesting - number of levels when pasring nested objects in query parameters (default: 3).
    • array.format - format for arrays in query parameters (possible values: 'bracket' (default), 'separator').
    • array.separator - if format is separator this field give you speficy which separator you want to use (default: ',').
    • breakHooks - whether or not hooks execution should be stopped immediately after first fail or all hooks should be performed in any case (default: true).
    • anchor - whether or not router should respect fragment (hash) value as an anchor if DOM element with appropriate id attribute is found (default: false).
    • scroll - whether or not router should restore scroll position upon the navigation (default: false).
    • focus - whether or not router should restore last focus on DOM element upon the navigation (default: false).

To change the preferences, just import and change them somewhere on top of your code:

import { prefs } from 'svelte-pathfinder';

prefs.scroll = true;
prefs.convertTypes = false;
prefs.array.format = 'separator';

Usually, you don't need to use second argument in $pattern() function and paramable store constructor, but in some cases its options can be useful for your goals:

  • loose - should the pattern match paths that are longer than the pattern itself? (default: false)
  • blank - should blank params object (with undeifned values) returned if pattern not match? (default: false)
  • sensitive - should be pattern case sensitive? (default: false)
  • decode - you can provide you own function to decode URL parameters. (default: decodeURIComponent will be used)

🕹 Usage

{#if params = $pattern('/products/:id')} <!-- eg. /products/1 -->
    <ProductView productId={} />
{:else if params = $pattern('/products')} <!-- eg. /products?page=2&q=Apple -->
    <ProductsList page={$} search={$query.q} />
    <NotFound path={$path} />

<Modal open={$fragment === '#login'}>
    <LoginForm />

    import { path, query, fragment, pattern } from 'svelte-pathfinder';
    let params;
{#if page}
    <svelte:component this={page.component} {params} />

    import { path, pattern } from 'svelte-pathfinder';
    import routes from './routes.js'; // [{ pattern: '/products', component: ProductsList }, ...]
    let params;
    $: page = routes.find((route) => params = $pattern(route.pattern)) || null; // match path pattens and get parsed params
    $: if ($path[0] === 'admin' && ! isAuthorized) { // check any specific segment of the path
        $path = '/forbidden'; // re-write whole path

Also, you able to use custom RegExp pattern instead of regular path-to-regexp pattern in $pattern() function. In this case, if you want to interprent some part of this RegExp pattern as an path parameter you need to use RegExp's named groups. For example, you need to make sure that path includes numeric identifier in second segment of the path:

{#if params = $pattern(/^\/todos\/(?<id>\d+)/)} <!-- will be matched only if second segment is a number -->
    <TodoDetail id={} />
{:else if params = $pattern('/todos/:action')} <!-- will be matched if second segment is NOT a number but any other value -->
    <TodoAction action={params.action} />
{:else if $pattern('/todos')}
    <TodoList  />

    import { pattern } from 'svelte-pathfinder';
    let params;

⚠️ Note: paramable stores still not support custom RegExp patterns. If you'll try to pass RegExp to paramable constructor it'll cause exception. Maybe similar support will be added in the future.

Performing updates of router state with optional side-effect to URL

    $ = 10; // set ?page=10 without changing or loose other query params
    $path[1] = 4; // set second segment of the path, e.g. /products/4
    $fragment = 'login'; // set url hash to #login 
    $state = { restoreOnBack: 'something' }; // set history record related state object
Directly bind & assign values to stores
<input bind:value={$query.q} placeholder="Search product...">
<button on:click={() => $fragment = 'login'}>Login</button>
<a href="/products/{}" on:click|preventDefault={e => $path[1] =}>

Creating stores to manipulating path parameters

// ./stores/params.js

import { paramable } from 'svelte-pathfinder';

export const productPageParams = paramable('/products/:category/:productId?');
<select bind:value={$params.category}>
    <option value="all">All</option>
    {#each categories as category}
        <option value={category.slug}>{}</option>
{#each products as product} 
    <a href="/products/{}" on:click|preventDefault={e => $params.productId =}>

    import { productPageParams as params } from './store/params';

Use with the other stores

import { derived } from 'svelte/store';
import asyncable from 'svelte-asyncable';
import { path, query } from 'svelte-pathfinder';

 import { productPageParams } from './store/params';

// with regular derived store

export const productData = derived(productPageParams, ($params, set) => {
    if ($params.productId}) {
            .then(res => res.json())
}, {});

// with svelte-asyncable

export const productsList = asyncable(async $query => {
    const res = await fetch(`/api/products${$query}`)
    return res.json();
}, undefined, [ query ]);

Using helper click

Auto-handling all links in the application.

<svelte:window on:click={click} />

<!-- links below will be handled by `click` helper -->

<nav class="navigate">
    <a href="/">Home</a>
    <a href="/products">Products</a>
    <a href="/about">About</a>

<!-- links below will be EXCLUDED from the navigation -->

<nav class="not-navigate">
    <a href="">External links</a>
    <a href="/shortlink/2hkjhrfwgsd" rel="external">Links with external rel</a>
    <a href="/products" target="_blank">Any links with target</a>
    <a href="/" target="_self">Any links with target even to _self</a>
    <a href="/path/" download>Download links</a>  
    <a href="">Mailto links</a>
    <a href="tel:+432423535">Tel links</a>
    <a href="/cart" on:click|preventDefault|stopPropagation={doSomething}>
        Just stop click event bubbling
    <a href="javascript:void(0)">Old style JS links</a>
    <a href="#hashOnly">Hash-only links</a>

    import { click } from 'svelte-pathfinder';

Using helpers goto and back

<button on:click={() => back()}>Back</button> 
<button on:click={() => goto('/cart?tab=overview')}>Open cart</button>

    import { goto, back } from 'svelte-pathfinder';

Using helper submit

<!-- handle GET-forms -->
<form on:submit={submit} action="/products" method="GET">
    <!-- all hidden fields will be propagated to $state by name attributes -->

    <input type="hidden" name="uid" value={$state.uid}>

    <!-- all visible fields will be propagated to $query by name attributes -->

    <input name="q" value={$query.q} placeholder="Title...">

    <select name="option" value={$query.option}>

    <!-- even pushed submit button will be propagated to $query by name attribute -->

    <button name="type" value="quick">Quick search</button>
    <button name="type" value="fulltext">Fulltext search</button>

    import { submit, query, state } from 'svelte-pathfinder';

Using hooks

Hook is a callback function which will be executed before actual router state update to perform some side-effects. Callback function receives 3 arguments: (1) upcoming store value, (2) current store value and (3) name of the store (simple 'path', 'query' or 'fragment' string).

If callback function return explicit false, specific router state update and subsequent navigation will be skipped. It can be useful for some kind of guards for specific router states.

Hooks applicable only for major stores such as path, query or fragment. Hook can be added using hook method of particular store which is returns cancel function:

onDestroy(path.hook(($path, $currentPath, name) => {

    if ($path[0] === 'my' && ! isAuthorized()) return false; // skip router state update

    // do some additional side-effect

    console.log(`Hook of ${name} performed`); // output: Hook of path performed

⚠️ Note: hooks are not pre-defined thing that's why it matters when and in what order the hooks are created in your app. When the hook is just added, the callback function will be executed instantly with upcoming value (first argument) equals null which means not actual state update, but that the hook was just cocked. You able to use this fact in some way:

onDestroy(query.hook(($query, $currentQuery, name) => {
    if ($query === null) {
        console.log(`Hook for ${name} is just added`);

Multiple hooks can be added to each particular store and they will be executed in order of adding hooks to the store. By default, if some hook returns explicit false value, execution process will be stoped immediately which is more optimized. If you need to perform all hooks in any case, just use prefs.breakHooks = false. In this case, all hooks will be executed but state still won't be updated and navigation won't be performed.

🔖 SSR support (highly experimental)


const express = require('express');

const app = express();
/* any other routes */
app.get('*', (req, res) => {
    const router = require('svelte-pathfinder/ssr')();
    const App = require('./App.svelte').default;


    const { html, head, css } = App.render({ router });

        <!DOCTYPE html>

⚠️ Note: you can't use pathfinder stores by just directly import it in SSR rendered applications (just like the other Svelte stores), because, in-fact, they're global to the entire server instance. To avoid it, just pass pathfinder instance to root component via props and use it in all components of application. For example using context:

<!-- App.svelte -->
<svelte:window on:click={}/>
    import { setContext } from 'svelte';

    export let router;
    setContext('router', router);
<!-- Nested.svelte -->
    import { getContext } from 'svelte';

    const { path } = getContext('router');

    function gotoSomething() {
        $path = '/something';

🚩 Assumptions

Optional side-effect (changing browser history and URL)

Router will automatically perform pushState to browser History API and listening popstate event if the following conditions are valid:

  • router works in browser and global objects are available (window & history).
  • router works in browser which is support pushState/popstate.
  • router works in top-level window and has no parent window (eg. iframe, frame, object,

If any condition is not applicable, the router will work properly but without side-effect (changing URL).

hashbang routing (#!)

Router will automatically switch to hashbang routing in the following conditions:

  • History API is not available.
  • web app has launched under file: protocol.
  • initial path contain exact file name with extension.

© License

MIT © PaulMaly



Last updated on 06 Aug 2023

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