Queueing with TypeScript

I’ve recently spent more time than I’d like to admit solving programming puzzles, and the queue data structure seems to be a reoccurring theme. JavaScript doesn’t have a built-in implementation, so I find myself copy/pasting the same few lines of code everywhere. I’ve decided it’s time to put that snippet somewhere more accessible.

I could just use the built-in array type directly with its push() and shift() methods, but that would be boring! I prefer to make the queue a first-class citizen in its own right. The idea is to hide the specific implementation details of “push” and “shift” behind more queue-like terminology: “enqueue” and “dequeue”. This makes the resultant code easier to read because the intentions are clearer.

export default class Queue<T> {
  constructor(private items: T[] = []) {}

  public enqueue(...items: T[]): void {
    this.items.push(...items);
  }

  public dequeue(): T {
    if (this.isEmpty()) {
      throw new Error("No items to dequeue!");
    }

    return this.items.shift() as T;
  }

  public isEmpty(): boolean {
    return this.size === 0;
  }

  public get size(): number {
    return this.items.length;
  }
}

Example usage:

import Queue from "./Queue";

const q = new Queue<string>();

console.assert(q.isEmpty());

q.enqueue("First item", "Second item");
q.enqueue("Another item");

console.assert(q.size === 3);

console.log(q.dequeue()); // "First item"

console.assert(q.size === 2);