@vicary/alpaca-sdk/esm/factory/createTokenBucket.js

A TypeScript SDK for the https://alpaca.markets REST API and WebSocket streams.

export const createTokenBucket = ({ capacity, fillRate } = {
    capacity: 200,
    fillRate: 3,
}) => {
    // Initialize tokens and last fill time
    let tokens = capacity;
    // Initialize last fill time
    let lastFillTime = Date.now();
    return {
        tokens,
        take: (count) => {
            // Calculate time delta
            const now = Date.now();
            const delta = (now - lastFillTime) / 1000;
            // Update last fill time and tokens
            lastFillTime = now;
            tokens = Math.min(capacity, tokens + delta * fillRate);
            // Check if tokens are available and take them if so
            // Otherwise, return false
            return tokens >= count ? ((tokens -= count), true) : false;
        },
    };
};