class CircularQueue {
    constructor (size) {
        this._max = size;
        this._start = 0;
        this._end = 0;
        this._length = 0;
        this._queue = new Array(size);
    }

    enq (item) {
        this._queue[this._end] = item;
        this._end = (this._end + 1) % this._max;

        if (this._length === this._max) {
            this._start = this._end;
        } else {
            this._length++;
        }
    }

    deq () {
        if (this._length) {
            const item = this._queue[this._start];
            this._start = (this._start + 1) % this._max;
            this._length--;

            return item;
        }
    }

    each (lambda) {
        for (let i = 0; i < this._length; i++) {
            const result = lambda(this._queue[(this._start + i) % this._max]);

            if (typeof result != 'undefined' && !result) // Stop iterating if "false" is returned
                break;
        }
    }
}