Airbnb Frontend Engineer Interview Questions

In building features around user-generated content, checking the integrity of uploaded texts like captions is essential for a polished interface. We want to verify if users have uploaded a string that can be rearranged into a palindrome.
Problem Statement: Given a string s, determine if it can be rearranged to form a palindrome. Return true if it can, and false otherwise.Example 1:
Input: s = "civic"
Output: true
Explanation: It can be rearranged to form a palindrome.Example 2:
Input: s = "ivicc"
Output: true
Explanation: It can be rearranged to form a palindrome.Constraints:
- 1 <= s.length <= 10^5
- s consists of only lowercase English letters.

In our messaging feature, we need to display user-friendly notifications by tracking the longest unique message sequence. This helps in showing the users their most recent unique messages efficiently.
Problem Statement: Given a string s, find the length of the longest substring without repeating characters. Return this length as an integer.Example 1:
Input: s = "abcabcbb"
Output: 3
Explanation: The answer is abc, with the length of 3.Example 2:
Input: s = "bbbbb"
Output: 1
Explanation: The answer is b, with the length of 1.Constraints:
- 0 <= s.length <= 5 * 10^4
- s consists of English letters, digits, symbols, and spaces.

As Airbnb scales, updating UI components such as listing details needs an efficient way to manage changes without unnecessary re-renders. A virtual DOM implementation optimizes rendering by comparing the current DOM state with an updated virtual representation, allowing for specific changes to be applied.
Problem Statement: Define a VDOM class that managed a virtual reality tree and provided methods for creating, updating, and rendering real DOM elements based on a virtual representation.### Class Definition:
- class VDOM:
- constructor() -> void:
Initializes a new Virtual DOM object.
- createElement(type: string, props: object, children: array) -> object:
Creates a virtual DOM node.
- diff(oldNode: object, newNode: object) -> object:
Compares two virtual nodes and returns the differences.
- render(node: object) -> HTMLElement:
Converts a virtual node into a real DOM element.### Example 1:
Input:

const vdom = new VDOM();
const vnode = vdom.createElement('div', { id: 'app' }, [vdom.createElement('span', {}, ['Hello'])]);
vdom.render(vnode);

Output:
'<div id="app"><span>Hello</span></div>'### Constraints:
- Element types should be strings, props should be an object, and children can be an array of virtual nodes or strings.

The Airbnb web application requires a robust client-side routing architecture to seamlessly navigate between various views without requiring full page reloads. This will enhance the overall user experience, allowing smooth transitions and dynamic content loading.
Problem Statement: Define a Router class that implements the necessary methods for managing routes effectively. The Router needs to handle registration of routes and navigating to these routes while storing the current state.### Class Definition:
- class Router:
- constructor() -> void:
Initializes a new Router object.
- register(path: string, callback: function) -> void:
Registers a new route with a corresponding callback function that is executed when the route is accessed.
- navigate(path: string) -> void:
Navigates to the given path, executing the associated callback.
- getCurrentRoute() -> string:
Returns the current path being displayed.### Example 1:
Input:

const router = new Router();
router.register('/home', () => console.log('Home Page'));
router.register('/about', () => console.log('About Page'));
router.navigate('/home');

Output:
'Hrme Page'### Constraints:
- The path should be a string representing the URL route.
- The callback function should be a valid JavaScript function.