A TypeScript class for tracking the number of requests within a sliding time window

window-counter.ts

class WindowCounter {
    private windowSize: number; // Window size in seconds
    private counter: Map<number, number>; // Map to store request counts
    private timer: any; // Timer reference

    constructor(windowSize: number) {
        this.windowSize = windowSize;
        this.counter = new Map();
        this.timer = null;
    }

    public start(): void {
        // Clear the existing counter and start the timer
        this.counter.clear();
        this.timer = setInterval(this.slideWindow, 1000); // Slide the window every second
    }

    public stop(): void {
        // Stop the timer
        if (this.timer) {
            clearInterval(this.timer);
            this.timer = null;
        }
    }

    public addRequest(): void {
        // Add a request count to the current second's index
        const currentSecond = Math.floor(Date.now() / 1000);
        const count = this.counter.get(currentSecond) || 0;
        this.counter.set(currentSecond, count + 1);
    }

    private slideWindow = (): void => {
        // Remove the oldest second's count from the counter map
        const currentSecond = Math.floor(Date.now() / 1000);
        const oldestSecond = currentSecond - this.windowSize;

        this.counter.delete(oldestSecond);
    };

    public getRequestCount(): number {
        // Calculate and return the total request count within the window
        let totalCount = 0;
        for (const count of this.counter.values()) {
            totalCount += count;
        }
        return totalCount;
    }
}

const counter = new WindowCounter(10); // 10-second window
counter.start();

// Simulate requests
counter.addRequest();
counter.addRequest();
counter.addRequest();

setTimeout(() => {
  counter.addRequest();
}, 5000); // Add a request after 5 seconds

setTimeout(() => {
  counter.addRequest();
  counter.stop();
  console.log(`Total requests in the last 10 seconds: ${counter.getRequestCount()}`);
}, 11000); // Stop the counter after 11 seconds and get the request count