JavaScript Certification Test Q&A (90 Questions) | AJAX, DOM, XSS, Syntax | Web Development

This document presents 90 curated exam questions and correct answers tailored for the JavaScript Certification Test 2025/2026, ideal for students, self-learners, and professionals preparing for JavaScript assessments or certifications. It provides a comprehensive review of core JavaScript concepts, web security, and client-side scripting techniques, making it a powerful resource for those pursuing careers in Web Development, Front-End Engineering, or Software Development. Key areas covered include: JavaScript syntax and structure, including variable declarations, data types (undefined, null), operators, functions, events, and casting DOM manipulation methods such as getElementById(), appendChild(), removeChild(), getAttribute(), and dynamic style updates AJAX operations, including the XMLHttpRequest object, open() method, and readyState values Cross-Site Scripting (XSS) vulnerabilities, prevention techniques, and client-side security best practices HTML5 integration, form validation, <canvas> usage, and input types like password and color Browser-specific behavior, plug-in use, and the role of JavaScript in client-server communication ECMAScript standards, JavaScript flavors, prototypes, inheritance, and object creation via constructors Students will also be introduced to cookie handling, jQuery basics (like $, event handlers), the navigator and window objects, the Math object, and error types (syntax, logic). This document is suitable for: University students in Computer Science, Web Development, Software Engineering, Information Systems Candidates preparing for JavaScript certification exams (vendor-neutral or platform-specific) Front-end developers seeking a refresher or practice guide Educators and trainers looking for ready-made question sets for testing or class quizzes Keywords: JavaScript, AJAX, DOM, XSS, jQuery, cookies, XMLHttpRequest, onblur, onchange, getElementById, localStorage, navigator, window, constructor, scripting vs programming, variable declaration, let vs const, HTML5, canvas, event handlers, Math object, JavaScript errors, JavaScript security, client-side validation, ECMAScript, prototype, browser compatibility