OpenAI Frontend Engineer Interview Questions

OpenAI's chatbot service needs to display a limited number of recent messages without overwhelming users. This exercise involves implementing a sliding window algorithm to fetch and manage the latest messages.
Given an array of messages and a number k, write a function that returns the last k messages sent to the chatbot.
Function Signature: function getLatestMessages(messages: string[], k: number): string[]
Example 1:
Input: getLatestMessages(["Hello", "How can I assist you?", "What is OpenAI?", "I love AI!"], 2)
Output: ['What is OpenAI?', 'I love AI!']
Explanation: The function returns the last two messages sent to the chatbot.Constraints:
- The messages array will have at least one message and at most 10^4 messages.
- k will be a positive integer not exceeding the number of messages.

In a rapidly evolving tech landscape, OpenAI needs robust data fetching capabilities to enhance user experience. This problem requires implementing a custom Promise that includes unique features tailored to OpenAI's needs.
Implement a custom Promise class complying with the following methods:
- resolve(value: any): void — resolve the promise with the given value.
- reject(reason: any): void — reject the promise with the given reason.
- then(onResolved: Function, onRejected: Function): Promise — register callbacks to receive either a resolved value or a rejection reason, and return a new promise resolving to the return value of the called callback.
Example 1:
Input: new Promise((resolve, reject) => { resolve('Success'); })
Output: 'Success'
Explanation: The promise resolves successfully with the value 'Success'.Constraints:
- Input values are any valid JavaScript data types.
- The promise must maintain a proper chain for chaining multiple then calls.

In developing OpenAI's products such as ChatGPT, a notification system for real-time updates on chat or model responses is essential. Design a system that allows publishing notifications and subscribing clients to receive them.
Define a class NotificationSystem that manages subscribers and notifications. Implement the following methods:
- subscribe(clientId: string, callback: Function): void — register a client with a callback to be notified.
- unsubscribe(clientId: string): void — remove a client from the list of subscribers.
- notify(message: string): void — send a message to all registered clients.
Example 1:
Input:
const notificationSystem = new NotificationSystem();
notificationSystem.subscribe('client1', (msg) => console.log(msg));
notificationSystem.notify('New message received!');
Output: New message received!
Explanation: Clients registered to receive notifications get the latest updates when notify is called.Constraints:
- Client IDs are unique strings.
- Each notification should reach all active subscribers.

OpenAI's applications such as Codex require efficient navigation without reloading entire pages. You are tasked with designing a client-side router for a web application.
Define a class Router that manages routes in an SPA. You should implement the following methods:
- addRoute(path: string, callback: Function): void — register a route with a specific path and callback function.
- navigate(path: string): void — navigate to the specified path and call the associated route's callback.
- getCurrentPath(): string — return the current path of the application.
Example 1:
Input:
const router = new Router();
router.addRoute('/home', () => console.log('Home Page'));
router.navigate('/home');
Output: Home Page
Explanation: Navigating to '/home' invokes the respective callback.Constraints:
- Path strings will always start with '/' and only contain alphanumeric characters and slashes.
- A route can only be registered once.