Implementing Throttling with JavaScript

throttling.js

class Throttler {
    constructor(maxRequests, period) {
        this.maxRequests = maxRequests;
        this.period = period;
        this.requestTimes = [];
    }

    addTokens() {
        const now = Date.now();
        this.requestTimes = this.requestTimes.filter(time => now - time < this.period);
    }

    allowRequest() {
        this.addTokens();
        if (this.requestTimes.length < this.maxRequests) {
            this.requestTimes.push(Date.now());
            return true;
        }
        return false;
    }

    delayRequest() {
        const waitTime = this.timeUntilNextAllowedRequest();
        if (waitTime > 0) {
            console.log(`Delaying request for ${waitTime}ms`);
            return new Promise(resolve => setTimeout(resolve, waitTime));
        }
        return Promise.resolve();
    }

    timeUntilNextAllowedRequest() {
        if (this.requestTimes.length === 0) {
            return 0;
        }
        const earliestRequestTime = this.requestTimes[0];
        const now = Date.now();
        return Math.max(0, (earliestRequestTime + this.period) - now);
    }
}

/* ================================
USAGE EXAMPLE
===================================
*/

// Initialize throttler
const throttler = new Throttler(10, 60000);  // 10 requests per 60 seconds

// Simulate requests using fetch
async function handleRequest() {
    if (throttler.allowRequest()) {
        console.log("Request allowed");
        // Simulate API request
        fetch('https://api.example.com/data')
            .then(response => response.json())
            .then(data => console.log(data))
            .catch(error => console.error('Error:', error));
    } else {
        await throttler.delayRequest();
        console.log("Request delayed, trying again");
        handleRequest();
    }
}

// Simulate requests every 2 seconds
for (let i = 1; i <= 20; i++) {
    setTimeout(handleRequest, i * 2000);  // Simulate a request every 2 seconds
}