Skip to main content

​
Class: SlidingWindowCounter

Defined in: throttle.ts:776 Sliding-window counter for per-key rate limiting. Maintains a current and previous window count per key and estimates the weighted request rate over the trailing windowMs ms by interpolating between the two windows. This provides smoother enforcement than a fixed-window counter (which lets twice the limit through across a window boundary) without the memory cost of a true sliding-window log. Calls a periodic cleanup every windowMs ms to drop stale entries — note that this means the limiter holds a Node timer for its entire lifetime. Long-lived processes are fine; for short-lived workers, manage instances explicitly or you’ll keep the event loop alive.

​
Example

const counter = new SlidingWindowCounter(60_000, 100); // 100 req/min
const decision = counter.check(`user:${userId}`);
if (!decision.allowed) return new Response("Too many requests", { status: 429 });

​
Constructors

​
Constructor

new SlidingWindowCounter(windowMs, maxRequests): SlidingWindowCounter
Defined in: throttle.ts:786

​
Parameters

windowMs
number Sliding-window length in milliseconds.
maxRequests
number Maximum allowed weighted count per window per key.

​
Returns

SlidingWindowCounter

​
Methods

​
check()

check(key): object
Defined in: throttle.ts:806 Atomically increment the counter for key and decide whether to allow the request based on the trailing weighted count.

​
Parameters

key
string

​
Returns

object { allowed, remaining, resetAt } where:
  • allowed — true if under the limit; false if rejected (counter is not incremented in this case).
  • remaining — best-effort lower bound on how many more requests fit in the current window for this key.
  • resetAt — Unix epoch ms when the current fixed window boundary rolls over.
allowed
allowed: boolean
remaining
remaining: number
resetAt
resetAt: number

​
getStats()

getStats(): object
Defined in: throttle.ts:877 Snapshot of currently-tracked keys.

​
Returns

object { activeKeys, keys }. The keys array is a one-shot copy and not kept in sync with future mutations.
activeKeys
activeKeys: number
keys
keys: readonly string[]

​
reset()

reset(key): void
Defined in: throttle.ts:852 Forget all state for key. The next check(key) starts fresh. Useful for admin/test reset paths and for clearing limits when a user upgrades to a higher tier.

​
Parameters

key
string

​
Returns

void