HTML5 HTML5 Web Workers 2

Question 1

What is a Shared Worker in HTML5, and how does it differ from a Dedicated Worker?

Accepted Answer

A Shared Worker can be accessed by multiple scripts from different windows or tabs of the same origin

Answer

Unlike a Dedicated Worker that is tied to one script, a Shared Worker can be shared across multiple browsing contexts (tabs, iframes) from the same origin.

Question 2

Which event fires on the main thread when a Web Worker encounters an uncaught error?

Accepted Answer

onerror

Answer

The 'onerror' event handler on the worker instance is triggered when the worker script throws an unhandled exception.

Question 3

What function is used to import external scripts inside a Web Worker?

Accepted Answer

importScripts('script.js')

Answer

importScripts() is a synchronous function available in worker scope that loads and executes one or more external JavaScript files.

Question 4

What is the key advantage of using Transferable Objects with postMessage() in Web Workers?

Accepted Answer

The data is transferred by reference (zero-copy), making it much faster for large data like ArrayBuffers

Answer

Transferable Objects like ArrayBuffers are moved (not copied) between threads, so the transfer cost is O(1) regardless of data size.

Question 5

Which Web Worker type is specifically designed to act as a network proxy and enable offline capabilities?

Accepted Answer

Service Worker

Answer

Service Workers act as a proxy between the browser and network, enabling features like offline caching, push notifications, and background sync.

HTML5 - HTML5 Web Development Practice Test

HTML5 - HTML5 Web Development Practice Test

HTML5 HTML5 Web Workers 2