1class CircularQueue {
2  constructor(size) {
3    this.queue = [];
4    this.read = 0;
5    this.write = 0;
6    this.max = size - 1;
7
8    while (size > 0) {
9      this.queue.push(null);
10      size--;
11    }
12  }
13
14  print() {
15    return this.queue;
16  }
17
18  enqueue(item) {
19    if (this.queue[this.write] === null) {
20      this.queue[this.write++] = item;
21
22      if (this.write > this.max) this.write = 0;
23      return item;
24    }
25    return null;
26  }
27
28  dequeue() {
29    if (this.queue[this.read] != null) {
30      let item = this.queue[this.read];
31      this.queue[this.read++] = null;
32      if (this.read > this.max) this.read = 0;
33      return item;
34    }
35    return null;
36  }
37}
38