Press n or j to go to the next uncovered block, b, p or k for the previous block.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 | 125x 125x 125x 125x 125x 125x 125x 125x 125x 125x 44x 14x 14x 14x 30x 130x 30x 30x 46x 46x 46x 51x 46x 46x 46x 46x 8x 8x 42x 42x 38x 46x 8x 8x 8x 30x 30x 30x 38x 30x 42x 42x 20x 20x 30x 26x 4x 30x 30x 30x 22x 22x 30x 30x 125x 125x 125x 120x | import { useCallback, useEffect, useMemo, useRef, useState } from "react";
import { useLatest } from "@usefy/use-latest";
import type { AsyncFnWithSignal } from "@usefy/use-async";
import type { AsyncState } from "@usefy/use-async-fn";
import { computePollingDelay, DEFAULT_POLLING_INTERVAL } from "./utils";
import type { UsePollingOptions, UsePollingReturn } from "./types";
/**
* Poll an async function on an interval, with **non-overlapping** self-scheduling
* ticks, imperative `pause`/`resume` (and `start`/`stop` aliases), a declarative
* `enabled` gate, and optional **exponential backoff** on consecutive failures.
*
* `usePolling` reuses the shared async-state shape of its batch-6 siblings
* (`useAsyncFn` / `useAsync`): the latest poll is exposed as
* `{ data, error, status, isLoading }` where `status` is the source of truth,
* `isLoading === status === "pending"`, and `data` is **retained** across later
* `pending`/`error` transitions. On top of that it adds polling-loop state:
* `isPolling` plus the controls.
*
* It is deliberately a **standalone** minimal state machine rather than a wrapper
* around `useAsync` — the same call `useAsync` itself made when it declined to
* wrap `useAsyncFn`. Driving `useAsync.execute()` from a timer would force us to
* suppress its `immediate`/mount auto-run and hijack its `onSuccess`/`onError`
* just to recover the per-poll success/failure signal that `execute()`'s
* ambiguous `T | undefined` return throws away (needed for backoff). Owning a
* tiny `AbortController` + call loop is clearer; the shared **types** keep the
* family consistent.
*
* ### No overlapping polls
* The next tick is scheduled with a self-rescheduling `setTimeout` **only after
* the current poll settles** — never a fixed `setInterval` that could stack
* requests when `fn` is slower than `interval`. There is at most one poll in
* flight at any moment.
*
* ### Controls & precedence
* - **`enabled`** (default `true`) is the declarative master gate. While it is
* `false` the loop never runs and `resume()` cannot start it.
* - **`pause`/`stop`** and **`resume`/`start`** are the imperative override
* *within* an enabled session. `isPolling === enabled && !paused`.
* - Pausing (or `enabled: false`, or unmounting) clears the pending timeout and
* **aborts** the in-flight poll via its `AbortSignal`; the aborted poll's
* result is discarded. If a poll was in flight when you pause, `status`
* settles back to its last resolved value (`success`/`error`/`idle`) and
* `isLoading` clears — it never sticks on `pending`.
*
* ### immediate
* `immediate` **defaults to `true`** — the first poll fires as soon as the loop
* starts (or resumes); the next tick waits `interval`. Pass `immediate: false`
* to wait one `interval` before the first poll.
*
* ### backoff
* With `backoff` enabled, the delay grows after each **consecutive** failure and
* resets to `interval` on the next success — `true` for exponential (`factor: 2`),
* `{ factor, maxInterval }` for a tuned exponential, or a `(failures, base) =>
* ms` function for full control.
*
* ### Safety
* SSR-safe (no timers or `AbortController` at module/render time — only inside
* effects, which never run on the server) and StrictMode-safe (the double-invoked
* mount effect tears the first loop down before starting the second, so exactly
* one self-scheduling loop is ever live — no runaway duplicate timers). `fn` and
* every option are read through refs, so an inline `fn` / changing options never
* restart the loop or go stale; only `enabled`/pause state starts and stops it.
*
* @typeParam T - The resolved data type of a single poll.
* @typeParam Args - The tuple of arguments forwarded to `fn` (after the signal).
* @typeParam E - The error type (defaults to `Error`).
*
* @param fn - The async function to poll. Receives `(signal, ...args)` — wire the
* {@link AbortSignal} into `fetch(url, { signal })` so a paused/stopped poll is
* truly cancelled.
* @param options - Optional `interval`, `immediate`, `enabled`, `backoff`, `args`,
* `initialData`, `onSuccess`, `onError`.
* @returns `{ data, error, status, isLoading, isPolling, pause, resume, start, stop }`.
*
* @example
* ```tsx
* function LiveStatus() {
* const { data, isPolling, pause, resume } = usePolling(
* async (signal: AbortSignal) => {
* const res = await fetch("/api/status", { signal });
* return (await res.json()) as { online: number };
* },
* { interval: 5000, immediate: true, backoff: { factor: 2, maxInterval: 30_000 } },
* );
*
* return (
* <div>
* <p>{data ? `${data.online} online` : "…"}</p>
* <button onClick={isPolling ? pause : resume}>
* {isPolling ? "Pause" : "Resume"}
* </button>
* </div>
* );
* }
* ```
*/
export function usePolling<T, Args extends unknown[] = unknown[], E = Error>(
fn: AsyncFnWithSignal<T, Args>,
options: UsePollingOptions<T, Args, E> = {},
): UsePollingReturn<T, E> {
const { enabled = true } = options;
const [state, setState] = useState<AsyncState<T, E>>(() => ({
data: options.initialData,
error: undefined,
status: "idle",
isLoading: false,
}));
// Imperative pause flag. `enabled` is the declarative master gate; the loop is
// active only while `enabled && !paused`.
const [paused, setPaused] = useState(false);
const active = enabled && !paused;
// Keep the latest fn/options in refs so the loop reads fresh values (a changed
// interval/args/inline fn applies on the next tick) without restarting, and so
// the controls stay referentially stable.
const latestFn = useLatest(fn);
const latestOptions = useLatest(options);
const timeoutRef = useRef<ReturnType<typeof setTimeout> | null>(null);
const controllerRef = useRef<AbortController | null>(null);
// Consecutive-failure counter driving backoff (reset to 0 on success / restart).
const failureCountRef = useRef(0);
useEffect(() => {
if (!active) {
// Loop gated off (pause / stop / enabled:false). If a poll was in flight
// it has been aborted by the previous effect's cleanup — settle a stuck
// `pending` so `isLoading` never sticks. This effect body never runs on
// unmount (only cleanups do), so it can't setState after unmount.
setState((prev) =>
prev.status === "pending"
? {
// A `pending` poll has already cleared `error`, so settle to the
// last successful value if there is one, otherwise back to idle.
...prev,
status: prev.data !== undefined ? "success" : "idle",
isLoading: false,
}
: prev,
);
return;
}
// A fresh loop instance. `cancelled` is closed over by this instance only,
// so StrictMode's mount→cleanup→mount double-invoke leaves exactly one live
// loop: the first instance's cleanup sets its own `cancelled` and clears the
// shared timeout before the second instance starts.
let cancelled = false;
const isLive = () => !cancelled;
// Restart with a clean backoff slate.
failureCountRef.current = 0;
const runTick = async () => {
Iif (!isLive()) return;
const controller = new AbortController();
controllerRef.current = controller;
setState((prev) => ({
data: prev.data,
error: undefined,
status: "pending",
isLoading: true,
}));
let result: T | undefined;
let failed = false;
let caught: E | undefined;
try {
const args = (latestOptions.current.args ?? []) as Args;
result = await latestFn.current(controller.signal, ...args);
} catch (err) {
failed = true;
caught = err as E;
} finally {
if (controllerRef.current === controller) controllerRef.current = null;
}
// The loop was torn down (pause / stop / enabled:false / unmount) while
// this poll was in flight — discard its result and schedule nothing.
if (!isLive()) return;
const baseInterval =
latestOptions.current.interval ?? DEFAULT_POLLING_INTERVAL;
if (failed) {
failureCountRef.current += 1;
setState((prev) => ({
data: prev.data,
error: caught,
status: "error",
isLoading: false,
}));
latestOptions.current.onError?.(caught as E);
} else {
failureCountRef.current = 0;
setState({
data: result,
error: undefined,
status: "success",
isLoading: false,
});
latestOptions.current.onSuccess?.(result as T);
}
scheduleNext(
computePollingDelay(
failureCountRef.current,
baseInterval,
latestOptions.current.backoff,
),
);
};
const scheduleNext = (delay: number) => {
Iif (!isLive()) return;
timeoutRef.current = setTimeout(() => {
timeoutRef.current = null;
void runTick();
}, delay);
};
// Start the loop: immediate first poll, or wait one interval.
if (latestOptions.current.immediate !== false) {
void runTick();
} else {
scheduleNext(latestOptions.current.interval ?? DEFAULT_POLLING_INTERVAL);
}
return () => {
cancelled = true;
if (timeoutRef.current !== null) {
clearTimeout(timeoutRef.current);
timeoutRef.current = null;
}
controllerRef.current?.abort();
controllerRef.current = null;
};
// `latestFn`/`latestOptions` are stable refs; only `active` starts/stops the loop.
}, [active, latestFn, latestOptions]);
const pause = useCallback(() => setPaused(true), []);
const resume = useCallback(() => setPaused(false), []);
return useMemo<UsePollingReturn<T, E>>(
() => ({
data: state.data,
error: state.error,
status: state.status,
isLoading: state.isLoading,
isPolling: active,
pause,
resume,
// `start`/`stop` are documented aliases of `resume`/`pause` — same identity.
start: resume,
stop: pause,
}),
[state, active, pause, resume],
);
}
|