`onParamValue`

The onParamValue function registers a listener that is called whenever a specific parameter value for a query changes.

onParamValue(
  queryId: MaybeGetter<IdOrNull>,
  paramId: MaybeGetter<IdOrNull>,
  listener: ParamValueListener,
  queriesOrQueriesId?: MaybeGetter<undefined | QueriesOrQueriesId>,
): void

	Type	Description
`queryId`	`MaybeGetter<IdOrNull>`	The `Id` of the query to listen to, or `null` to listen to any query.
`paramId`	`MaybeGetter<IdOrNull>`	The `Id` of the parameter to listen to, or `null` to listen to any parameter.
`listener`	`ParamValueListener`	The function to call when the parameter value changes.
`queriesOrQueriesId?`	`MaybeGetter<undefined \| QueriesOrQueriesId>`	The `Queries` object to use, or its `Id`.
returns	`void`	This has no return value.

Example

This example registers a Svelte listener and responds to a TinyBase change.

App.svelte

<svelte:options runes={true} />

<script>
  import {onParamValue} from 'tinybase/ui-svelte';

  let {queries} = $props();
  let seen = $state('');

  onParamValue('petColors', 'species', () => (seen = 'changed'), queries);
</script>

{seen}

import {flushSync, mount} from 'svelte';
import {createQueries, createStore} from 'tinybase';
import App from './App.svelte';

const store = createStore()
  .setTables({
    pets: {
      fido: {species: 'dog', color: 'brown', sold: false, next: 'felix'},
      felix: {species: 'cat', color: 'black', sold: true},
    },
    species: {dog: {price: 5}, cat: {price: 4}},
  })
  .setValues({open: true, employees: 3});
const queries = createQueries(store).setQueryDefinition(
  'petColors',
  'pets',
  ({select}) => select('color'),
);
const app = document.body.appendChild(document.createElement('div'));
flushSync(() => mount(App, {target: app, props: {queries}}));
flushSync(() => {
  queries.setParamValue('petColors', 'species', 'dog');
});
flushSync();
console.log(app.textContent);
// -> 'changed'

Since

v8.1.0