trackQuery

Track specific query parameters in the URL with schema validation. When the specified parameters appear in the URL and match the schema, the tracker enters; when they're removed, invalid, or no selected route is open, it exits.

API

trackQuery<T extends ZodType>(config: {
  controls: RouterControls;
  routes?: Route[];
  parameters: T;
}): QueryTracker<T>

Config

Parameter	Type	Description
controls	RouterControls	Controls that own query navigation
routes	Route[]	Optional OR filter based on each route's $isOpened store
parameters	ZodType	Zod schema for query parameter validation

When navigation switches between registered routes in routes, the tracker keeps the activity change atomic: it does not emit a transient exited while the target route is pending. The target query is validated after that route opens. If target activation fails, an already entered tracker exits.

Returns

QueryTracker<T> with the following properties:

Property	Type	Description
$state	Store<QueryTrackerState<T>>	Current inactive, pending, or entered state
enter	Event<z.infer<T>>	Programmatically add parameters to URL
entered	Event<z.infer<T>>	Fires when parameters match schema
exit	Event<{ ignoreParams?: string[] } | void>	Programmatically remove parameters
exited	Event<void>	Fires when parameters no longer match

$state is evaluated from the current stores, so it is already accurate when the tracker is created after history initialization or read from a Fork. Its states are { status: 'inactive' }, { status: 'pending' }, and { status: 'entered', params }. Use the store when current state matters; entered and exited describe transitions observed after tracker creation and do not replay a state that already existed. For late creation, sample $state with the consumer's own lifecycle event.

enter accepts only keys declared by the schema and URL-compatible values: string, null, or ordered arrays of those values. Convert numbers, dates, booleans, and other domain values before calling enter. entered publishes the schema's parsed output, so a schema transform may expose domain values to listeners without widening the URL input contract.

enter merges only the supplied schema keys into the current query. exit removes schema-owned keys while preserving unrelated keys; pass ignoreParams to preserve selected keys explicitly. Route activation and deactivation use the same ownership rules.

The query matrix covers flags, repeated keys, empty arrays, reserved-character encoding, path-only navigation, explicit clears, route-less and OR-filtered trackers, transformed schemas, enter/exit ownership, and adapter round trips.

Usage

Basic Query Tracking

import {
  createRoute,
  createRouter,
  createRouterControls,
  trackQuery,
} from '@effector/router';
import { z } from 'zod';

const searchRoute = createRoute({ path: '/search' });

const controls = createRouterControls();
const router = createRouter({
  routes: [searchRoute],
  controls,
});

// Track search query parameter
const searchTracker = trackQuery({
  controls,
  parameters: z.object({
    q: z.string(),
  }),
  routes: [searchRoute],
});

// Listen when search query appears
sample({
  clock: searchTracker.entered,
  fn: (params) => console.log('Search query:', params.q),
});

// Listen when search query is removed
sample({
  clock: searchTracker.exited,
  fn: () => console.log('Search cleared'),
});

Read the tracker when the application starts

Compose application-readiness policy from the current $state and an ordinary Effector clock:

import {
  createRouter,
  createRouterControls,
  createRoute,
  trackQuery,
} from '@effector/router';
import { sample } from 'effector';
import { z } from 'zod';
import { acceptInvitationFx } from '@shared/api';
import { appStarted } from '@shared/global';

const familyRoute = createRoute({ path: '/search' });
const controls = createRouterControls();
const router = createRouter({
  routes: [familyRoute],
  controls,
});

const invitationTracker = trackQuery({
  controls,
  routes: [familyRoute],
  parameters: z.object({
    inviteId: z.string(),
  }),
});

sample({
  clock: appStarted,
  source: invitationTracker.$state,
  filter: (
    state,
  ): state is { status: 'entered'; params: { inviteId: string } } =>
    state.status === 'entered',
  fn: (state) => state.params,
  target: acceptInvitationFx,
});

Add/Remove Query Parameters

import { z } from 'zod';

const filterTracker = trackQuery({
  controls,
  parameters: z.object({
    status: z.enum(['active', 'inactive']),
    category: z.string(),
  }),
  routes: [productsRoute],
});

// Add filters to URL
filterTracker.enter({
  status: 'active',
  category: 'electronics',
});
// URL becomes: /products?status=active&category=electronics

// Remove all tracked parameters
filterTracker.exit();
// URL becomes: /products

// Remove tracked parameters but keep others
filterTracker.exit({ ignoreParams: ['page'] });
// Removes status and category, keeps page param

Pagination

import { z } from 'zod';

const paginationTracker = trackQuery({
  controls,
  parameters: z.object({
    page: z.string().regex(/^\d+$/),
    limit: z.string().regex(/^\d+$/),
  }),
  routes: [listRoute],
});

// Go to page 2
paginationTracker.enter({ page: '2', limit: '20' });

// Reset to first page
paginationTracker.exit();

Optional Parameters

import { z } from 'zod';

const advancedSearchTracker = trackQuery({
  controls,
  parameters: z.object({
    q: z.string(),
    tags: z.array(z.string()).optional(),
    minPrice: z.string().optional(),
    maxPrice: z.string().optional(),
  }),
  routes: [searchRoute],
});

// Required query only
advancedSearchTracker.enter({ q: 'laptop' });

// With optional parameters
advancedSearchTracker.enter({
  q: 'laptop',
  tags: ['electronics', 'computers'],
  minPrice: '500',
  maxPrice: '2000',
});

Multiple Trackers

import { z } from 'zod';

// Track search independently
const searchTracker = trackQuery({
  controls,
  parameters: z.object({ q: z.string() }),
  routes: [searchRoute],
});

// Track filters independently
const filterTracker = trackQuery({
  controls,
  parameters: z.object({
    category: z.string(),
    status: z.string(),
  }),
  routes: [searchRoute],
});

// Track sort independently
const sortTracker = trackQuery({
  controls,
  parameters: z.object({
    sort: z.enum(['asc', 'desc']),
    sortBy: z.string(),
  }),
  routes: [searchRoute],
});

// Each tracker manages its own parameters
searchTracker.enter({ q: 'phone' });
filterTracker.enter({ category: 'mobile', status: 'active' });
sortTracker.enter({ sort: 'asc', sortBy: 'price' });
// URL: /search?q=phone&category=mobile&status=active&sort=asc&sortBy=price

With Router Controls

import { createRouterControls, trackQuery } from '@effector/router';
import { z } from 'zod';

const controls = createRouterControls();

// Omitting routes keeps the tracker active for every location.
const themeTracker = trackQuery({
  controls,
  parameters: z.object({
    theme: z.enum(['light', 'dark']),
  }),
});

// Theme parameter works on all routes
themeTracker.enter({ theme: 'dark' });

React Integration

import { useUnit } from 'effector-react';
import { z } from 'zod';

const filterTracker = trackQuery({
  controls,
  parameters: z.object({
    search: z.string(),
    category: z.string().optional(),
  }),
  routes: [productsRoute],
});

function ProductFilters() {
  const [search, setSearch] = useState('');
  const [category, setCategory] = useState('');

  const handleApplyFilters = () => {
    filterTracker.enter({
      search,
      ...(category && { category }),
    });
  };

  const handleClearFilters = () => {
    filterTracker.exit();
    setSearch('');
    setCategory('');
  };

  return (
    <div>
      <input
        value={search}
        onChange={(e) => setSearch(e.target.value)}
        placeholder="Search..."
      />
      <select value={category} onChange={(e) => setCategory(e.target.value)}>
        <option value="">All Categories</option>
        <option value="electronics">Electronics</option>
        <option value="clothing">Clothing</option>
      </select>
      <button onClick={handleApplyFilters}>Apply</button>
      <button onClick={handleClearFilters}>Clear</button>
    </div>
  );
}

Store Parsed Query Parameters

The entered event carries the parsed z.infer<T> value, so it can update a store directly:

import { createStore, sample } from 'effector';
import { z } from 'zod';

const searchTracker = trackQuery({
  controls,
  parameters: z.object({
    q: z.string(),
    page: z.coerce.number().default(1),
  }),
  routes: [searchRoute],
});

const $searchQuery = createStore({ q: '', page: 1 });

sample({
  clock: searchTracker.entered,
  target: $searchQuery,
});

sample({
  clock: searchTracker.exited,
  target: $searchQuery.reinit,
});

Load Data on Query Change

import { sample } from 'effector';
import { z } from 'zod';

const searchTracker = trackQuery({
  controls,
  parameters: z.object({
    q: z.string(),
    page: z.string().optional(),
  }),
  routes: [searchRoute],
});

const loadSearchResultsFx = createEffect(
  async (params: { q: string; page?: string }) => {
    return await fetchSearchResults(params);
  },
);

// Load results when search query is entered
sample({
  clock: searchTracker.entered,
  target: loadSearchResultsFx,
});

// Clear results when search is exited
sample({
  clock: searchTracker.exited,
  target: $searchResults.reinit,
});

Validation Handling

import { z } from 'zod';

const strictPaginationTracker = trackQuery({
  controls,
  parameters: z.object({
    page: z
      .string()
      .regex(/^\d+$/)
      .refine((val) => parseInt(val) > 0),
    limit: z.enum(['10', '20', '50', '100']),
  }),
  routes: [listRoute],
});

// ✅ Valid - tracker enters
// URL: /list?page=1&limit=20

// ❌ Invalid - tracker won't enter or will exit
// URL: /list?page=0&limit=20      (page must be > 0)
// URL: /list?page=abc&limit=20    (page must be number)
// URL: /list?page=1&limit=30      (limit must be 10/20/50/100)

How It Works

1. Validation: Continuously validates current query parameters against the schema
2. Entered: When parameters match the schema, entered fires with validated data
3. Exited: When parameters no longer match (removed or invalid), exited fires
4. Route Filtering: If routes is specified, only tracks when those routes are active

Best Practices

Use Specific Schemas

Define precise validation rules:

// ✅ Good: Specific validation
const tracker = trackQuery({
  controls,
  parameters: z.object({
    page: z
      .string()
      .regex(/^\d+$/)
      .refine((val) => parseInt(val) > 0),
    sortBy: z.enum(['name', 'date', 'price']),
  }),
  routes: [listRoute],
});

// ❌ Bad: Too permissive
const tracker = trackQuery({
  controls,
  parameters: z.object({
    page: z.any(),
    sortBy: z.string(),
  }),
  routes: [listRoute],
});

Scope to Routes

Only track query parameters for relevant routes:

// ✅ Good: Scoped to search route
const searchTracker = trackQuery({
  controls,
  parameters: z.object({ q: z.string() }),
  routes: [searchRoute],
});

// ❌ Bad: Tracks on all routes (unless intended)
const searchTracker = trackQuery({
  controls,
  parameters: z.object({ q: z.string() }),
});

Separate Concerns

Create separate trackers for different parameter groups:

// ✅ Good: Separate trackers for independent concerns
const searchTracker = trackQuery({
  controls,
  parameters: z.object({ q: z.string() }),
  routes: [searchRoute],
});

const paginationTracker = trackQuery({
  controls,
  parameters: z.object({ page: z.string() }),
  routes: [searchRoute],
});

// ❌ Bad: Mixed concerns
const mixedTracker = trackQuery({
  controls,
  parameters: z.object({
    q: z.string(),
    page: z.string(),
    theme: z.string(),
  }),
  routes: [searchRoute],
});

See Also

• createRouter - Register routes and bind controls to history
• createRouterControls - Create controls for standalone operators