`await-semaphore` is an ES6 promise-based semaphore and mutex implementation for JavaScript and TypeScript, providing three usage styles: async/await, thunk-based automatic acquire/release, and promise chaining. It's designed for developers who need to control concurrency in asynchronous code, such as limiting parallel API requests or protecting critical sections in Node.js or browser environments. The library includes both `Semaphore` for general counting semaphores and `Mutex` as a convenience wrapper for binary semaphores.