use-search-param-state

A hook to synchronize React state with URL search params.

Basic usage

1import { useSearchParamState } from "use-search-param-state";
2
3function Root() {
4  return (
5    <SearchParamStateProvider>
6      <Demo />
7    </SearchParamStateProvider>
8  );
9}
10
11function Demo() {
12  const [counterState, setCounterState] = useSearchParamState("counter", 0);
13}

or

1import { useSearchParamState } from "use-search-param-state";
2import { z } from "zod";
3
4function Root() {
5  // this `sanitize` is used by every instance of `useSearchParamState`
6  const sanitize = (unsanitized: string) => yourSanitizer(unsanitized);
7  return (
8    <SearchParamStateProvider buildOptions={{ sanitize }}>
9      <Demo />
10    </SearchParamStateProvider>
11  );
12}
13
14function Demo() {
15  const schema = z.number();
16  const [counterState, setCounterState] = useSearchParamState("counter", 0, {
17    validate: schema.parse,
18  });
19}

Explanation

On the first render, useSearchParamState will read from the counter URL search param.

By default, the counter search param is read using window.location.href. If the window object is undefined, useSearchParamState will use the serverSideURL instead to read from the URL. If serverSideURL is also not provided, counterState will be set to the initial state (i.e. 0).

If the counter search param does not exist (i.e. URLSearchParams.get returns null), counterState will be set to the initial state.

Once the counter search param is accessed, the raw string is passed to sanitize, the output of sanitize is passed to parse, and finally the output of parse is passed to validate. Note that useSearchParamState aims to return a parsed value, not a stringified value!

If sanitize, parse, or validate throw an error, the onError option is called and counterState will be set to the initial state.

If none of sanitize, parse, and validate throw an error, counterState is set to the sanitized, parsed, and validated value in the counter search param.

Note that useSearchParamState intentionally does not set the URL on the first render, since this can cause an infinite loop when navigating backwards. For example, say we have a url /blog with a search param search defaulted to hello. Navigating to /blog would immediately add ?search=hello to the URL, so navigating backwards would push /blog ... which would add ?search=hello to the URL again!

---

When setting the state using setCounterState, the new state is stringified using the stringify option, and the URL is set using the pushState option.

If deleteEmptySearchParam is true and isEmptySearchParam returns true, the search param will be deleted from the URL.

However, if stringify or pushState throw an error, onError will be called and the URL will not be set. Additionally, if the rollbackOnError option is set to true, counterState will be set to its value prior to when setCounterState was called. Otherwise, counterState will retain its new value, and the counter URL search param will be out of sync with counterState. The latter behavior is the default, since local state tends to take precedence over URL state.

Note that multiple instances of useSearchParamState that read from the same URL search param will be kept in-sync thanks to the SearchParamStateProvider wrapping your app.

Options

useSearchParamState accepts the following options:

1interface UseSearchParamStateOptions<TVal> {
2  stringify?: (valToStringify: TVal) => string;
3  sanitize?: (unsanitized: string) => string;
4  parse?: (unparsed: string) => TVal;
5  validate?: (unvalidated: unknown) => TVal;
6  deleteEmptySearchParam?: boolean;
7  isEmptySearchParam?: (searchParamVal: TVal) => boolean;
8  serverSideURL?: string;
9  rollbackOnError?: boolean;
10  pushState?: (stringifiedSearchParams: string) => void;
11  onError?: (e: unknown) => void;
12}

Note that sanitize, parse, and validate run in the following order when pulling the initial state from the URL search param:

1// simplified
2const rawSearchParam = new URLSearchParams(window.location.search).get(
3  searchParam,
4);
5const sanitized = options.sanitize(rawSearchParam);
6const parsed = options.parse(sanitized);
7const validated = options.validate(parsed);
8
9return validated;

sanitize

A function with the following type: (unsanitized: string) => string.

sanitize is called with the raw string pulled from the URL search param.

If sanitize throws an error, onError will be called and useSearchParamState will return the initial state.

sanitize can be passed directly to useSearchParamState, or to SearchParamStateProvider. When a sanitize option is passed to both, only the sanitize passed to useSearchParamState will be called.

sanitize has no default value.

parse

A function with the following type: (unparsed: string) => TVal.

The result of sanitize is passed as the unparsed argument to parse.

If parse throws an error, onError will be called and useSearchParamState will return the initial state.

parse can be passed directly to useSearchParamState, or to SearchParamStateProvider. When a parse option is passed to both, only the parse passed to useSearchParamState will be called.

parse defaults to:

1export function defaultParse(unparsed: string) {
2  // JSON.parse errors on "undefined"
3  if (unparsed === "undefined") return undefined;
4
5  // Number parses "" to 0
6  if (unparsed === "") return "";
7
8  // Number coerces bigints to numbers
9  const maybeNum = Number(unparsed);
10  if (!Number.isNaN(maybeNum)) return maybeNum;
11
12  try {
13    return JSON.parse(unparsed);
14  } catch {
15    return unparsed;
16  }
17}

validate

A function with the following type: (unvalidated: unknown) => TVal.

The result of parse is passed as the unvalidated argument to validate.

validate is expected to validate and return the unvalidated argument passed to it (presumably of type TVal), or throw an error. If validate throws an error, onError will be called and useSearchParamState will return the initial state.

validate has no default value.

deleteEmptySearchParam

A boolean.

When calling the setState function returned by useSearchParamState, if deleteEmptySearchParam is true and isEmptySearchParam returns true, the search param will be deleted from the URL.

deleteEmptySearchParam defaults to false.

isEmptySearchParam

A function with the following type: (searchParamVal: TVal) => boolean;.

When calling the setState function returned by useSearchParamState, if deleteEmptySearchParam is true and isEmptySearchParam returns true, the search param will be deleted from the URL.

isEmptySearchParam defaults to:

1function defaultIsEmptySearchParam<TVal>(searchParamVal: TVal) {
2  return (
3    searchParamVal === null ||
4    searchParamVal === undefined ||
5    searchParamVal === ""
6  );
7}

stringify

A function with the following type: (valToStringify: TVal) => string.

stringify is used to dehydrate the search param state before setting the stringified value in the URL.

If stringify throws an error, onError will be called and the URL will not be set.

stringify can be passed directly to useSearchParamState, or to SearchParamStateProvider. When a stringify option is passed to both, only the stringify passed to useSearchParamState will be called.

stringify defaults to:

1function defaultStringify<TVal>(valToStringify: TVal) {
2  // avoid wrapping strings in quotes
3  if (typeof valToStringify === "string") return valToStringify;
4  return JSON.stringify(valToStringify);
5}

serverSideURL

A value of type string - any valid string input to the URL constructor.

When passed, serverSideURL will be used when window is undefined to access the URL search param. This is useful for generating content on the server, i.e. with Next.js:

1import url from "url";
2
3export const getServerSideProps: GetServerSideProps = ({ req }) => {
4  const protocol = req.headers["x-forwarded-proto"] || "http";
5  const serverSideURL = `${protocol}://${req.headers.host}${req.url}`;
6
7  return {
8    props: { serverSideURL },
9  };
10};
11
12export default function Home({
13  serverSideURL,
14}: InferGetServerSidePropsType<typeof getServerSideProps>) {
15  const [counter] = useSearchParamState("counter", 0, {
16    serverSideURL,
17  });
18
19  // has the correct value for `counter` when rendered on the server
20  return <div>counter: {counter}</div>;
21}

Note that if no serverSideURL option is passed and window is undefined, you may encounter hydration errors.

rollbackOnError

A boolean.

When calling the setState function returned by useSearchParamState, pushState will be called to set the URL search param with the latest React state value. If setting the search param in the URL throws an error, and rollbackOnError is set to true, the local React state will "rollback" to its previous value.

rollbackOnError can be passed directly to useSearchParamState, or to SearchParamStateProvider. When a rollbackOnError option is passed to both, only the rollbackOnError passed to useSearchParamState will be called.

rollbackOnError defaults to false.

pushState

A function with the following type: (href: string) => void.

pushState is called to set the search param state in the URL.

pushState can be passed directly to useSearchParamState, or to SearchParamStateProvider. When a pushState option is passed to both, only the pushState passed to useSearchParamState will be called.

pushState defaults to:

1function defaultPushState(stringifiedSearchParams: string) {
2  window.history.pushState({}, "", stringifiedSearchParams);
3}

onError

A function with the following type: (e: unknown) => void.

Most actions in useSearchParamState are wrapped in a try catch block - onError is called whenever the catch block is reached. This includes situations when sanitize, parse, or validate throw an error.

onError can be passed directly to useSearchParamState, or to SearchParamStateProvider. When an onError option is passed to both, both the functions will be called.

Testing

The best approach to test uses of useSearchParamState is by mocking the window.location property directly in your tests:

1Object.defineProperty(window, "location", {
2  writable: true,
3  value: { search: "?counter=1" },
4});

If you mutate window.location directly, i.e.

1window.location = { search: "?counter=1" };

You may receive an error that window.location is read-only.

---

Also note that since this library utilizes context, you'll need to use a wrappedRender like the following when testing components outside your root:

1import { render, RenderOptions } from "@testing-library/react";
2
3function wrappedRender(
4  ui: React.ReactElement,
5  options?: Omit<RenderOptions, "wrapper">,
6) {
7  const wrapper = ({ children }: { children: React.ReactNode }) => (
8    <SearchParamStateProvider>{children}</SearchParamStateProvider>
9  );
10
11  return render(ui, { wrapper, ...options });
12}

If useSearchParamState is used without a parent SearchParamStateProvider, it'll throw an error.