Promise based Lock and Queue

promise_queue.js

/**
 * Асинхронная очередь с локами на чтение/запись
 */
class Queue {
    constructor() {
        this.queue = [];
        this.readLock = new Lock();
        this.writeLock = new Lock();
        this.setEmpty();
    }

    setEmpty() {
        this.notEmpty = new Promise(resolve => this.setNotEmpty = resolve);
    }

    async put(task) {
        let unlock = await this.writeLock.acquire();

        this.queue.push(task);
        this.setNotEmpty();

        unlock();
    }

    async get() {
        let unlock = await this.readLock.acquire();

        await this.notEmpty;
        let task = this.queue.shift();
        this.queue.length || this.setEmpty();

        unlock();
        return task;
    }
}

class Lock {
    constructor() {
        this.promise = Promise.resolve();
    }

    acquire() {
        let unlockNext;
        let willLock = new Promise(resolve => unlockNext = resolve);
        let unlock = this.promise.then(() => unlockNext);
        this.promise = this.promise.then(() => willLock);
        return unlock;
    }
}


/***************** TEST *********************/

queue = new Queue();
(async () => console.log('POP1', await queue.get()))();
(async () => console.log('POP2', await queue.get()))();
queue.put(1);

// Output: 
// POP 1

listenQueue = async(queue) => {
    let task;
    while(task = await queue.get()) {
        console.log('TASK', task);
    }
};

listenQueue(queue);
queue.put(2);
queue.put(3);

// Output: 
// POP 2
// TASK 3

(async () => console.log('POP3', await queue.get()))();
(async () => console.log('POP4', await queue.get()))();

queue.put('hello1');
queue.put('hello2');
queue.put('hello3');
queue.put('hello4');

// Output: 
// TASK hello1
// POP3 hello2
// POP4 hello3
// TASK hello4