Generic TypeScript Queue

Common errors

• Argument of type 'number' is not assignable to parameter of type 'string'.

  cause Attempting to create or add a value of an incorrect type to a generic queue that was initialized with a different type.
  fix Ensure the types of values being added match the generic type parameter of the `Queue`. Example: `let queue = new Queue<string>(); queue.enqueue(123);` will cause this error. Correct by using `queue.enqueue('hello');` or by initializing the queue as `new Queue<any>()`.

• Property 'bar' does not exist on type 'undefined'.

  cause Trying to access properties of an element (like `front`) when the queue is empty, resulting in `undefined`.
  fix Add a check for an empty queue before accessing elements: `if (queue.length > 0) { console.log(queue.front.bar); }`.

Warnings

• gotcha Type Mismatch during Queue Initialization or Enqueuing: The `Queue` class uses generics for type safety. Attempting to initialize or enqueue values that do not match the specified generic type `T` will result in a TypeScript compilation error.
  Fix: Ensure all values passed to the `Queue` constructor or `enqueue` method conform to the generic type `T` declared for the queue instance. If varying types are expected, declare the queue with `Queue<any>`.
• gotcha Empty Queue Operations: Attempting to access `queue.front` on an empty queue will return `undefined`.
  Fix: Always check `queue.length > 0` or specifically check if `queue.front` is `undefined` before attempting to use the returned value to avoid unexpected runtime errors.
• gotcha CommonJS (require) vs. ESM (import) Syntax: While the package README shows both `require` and `import` for `Queue`, modern TypeScript projects and Node.js environments increasingly favor ESM `import` statements. Using `require` might indicate an older project setup or specific configuration.
  Fix: For new TypeScript projects, prefer `import { Queue } from 'queue-typescript';`. If using CommonJS, ensure your `tsconfig.json` `module` option is set appropriately (e.g., `"CommonJS"`).

Install

• npm install queue-typescript npm
• yarn add queue-typescript yarn
• pnpm add queue-typescript pnpm

Imports

• Queue

  import { Queue } from 'queue-typescript';

  This is the standard ESM import for TypeScript projects.
• Queue
  wrong:

  import Queue from 'queue-typescript'; // Incorrect default import

  correct:

  const { Queue } = require('queue-typescript');

  While CommonJS `require` works, modern TypeScript projects typically use ESM imports. The `Queue` class is a named export, not a default export.
• Queue (Type Usage)
  wrong:

  let myQueue: Queue = new Queue(); // Lacks generic type parameter

  correct:

  let myQueue: Queue<string> = new Queue<string>();

  Always specify the generic type parameter (e.g., `<string>`) when declaring or instantiating a `Queue` to leverage TypeScript's type safety features fully.

Quickstart

This example demonstrates how to create, initialize, enqueue items into, and iterate through a generic TypeScript Queue, showcasing its iterable protocol support.

import { Queue } from 'queue-typescript';

// Create a new queue initialized with numbers
let numberQueue = new Queue<number>(10, 20, 30);
console.log('Initial queue length:', numberQueue.length); // Expected: 3
console.log('Front element:', numberQueue.front); // Expected: 10

// Enqueue new items
numberQueue.enqueue(40);
numberQueue.enqueue(50);
console.log('Queue after enqueuing:', numberQueue.length); // Expected: 5

// Iterate through the queue using for...of
console.log('Queue elements:');
for (const item of numberQueue) {
  console.log(item);
}
// Expected: 10, 20, 30, 40, 50 (each on a new line)

// Deconstruct the queue
const [first, second, ...rest] = numberQueue;
console.log('First element (deconstructed):', first);   // Expected: 10
console.log('Second element (deconstructed):', second); // Expected: 20
console.log('Remaining elements (deconstructed):', rest); // Expected: [30, 40, 50] (or similar array representation)