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Developer Expert Exam
Question 1. Which ES6 feature allows you to write functions with a shorter syntax and lexical binding of this? A) Promises B) Arrow functions C) Destructuring D) Modules Answer: B Explanation: Arrow functions provide a concise syntax for functions and lexically bind this to the surrounding context, making them especially useful in callbacks and nested functions. Question 2. What is the primary benefit of using let and const over var in JavaScript?
Developer Expert Exam
A) They are faster to execute B) They provide block scope and prevent redeclaration C) They automatically handle errors D) They are compatible with older browsers Answer: B Explanation: let and const are block-scoped variables introduced in ES6, preventing variable hoisting and redeclaration issues common with var. Question 3. Which JavaScript concept involves functions remembering the variables from their lexical scope even after the outer function has executed? A) Closure B) Prototype chain C) Call stack
Developer Expert Exam
Explanation: Inside a regular function, this refers to the object that invoked the function. In strict mode, it can be undefined. Question 5. Which inheritance pattern is primarily used in JavaScript to implement object-oriented programming? A) Classical inheritance via classes B) Prototypal inheritance C) Multiple inheritance D) Interface inheritance Answer: B Explanation: JavaScript uses prototypal inheritance, where objects inherit directly from other objects via prototypes.
Developer Expert Exam
Question 6. Which debugging technique is most effective for catching runtime errors in JavaScript? A) Minification B) Using browser developer tools and console logs C) Bundling scripts D) Lazy loading scripts Answer: B Explanation: Browser developer tools allow real-time inspection, breakpoints, and console logs to identify and diagnose runtime errors effectively. Question 7. Which HTML attribute is best suited for deferring the loading of JavaScript to improve performance?
Developer Expert Exam
D) All of the above Answer: D Explanation: Minification reduces file size, bundling combines multiple files into one, and code splitting loads only necessary code, all enhancing performance. Question 9. Which strategy helps in reducing the critical rendering path in a web page? A) Loading JavaScript synchronously in the head B) Lazy loading non-essential JavaScript and CSS C) Inline all scripts in HTML D) Avoiding CSS files Answer: B
Developer Expert Exam
Explanation: Lazy loading non-critical resources allows the browser to render the page faster by prioritizing essential assets. Question 10. What is a common security risk associated with executing unsanitized user input in JavaScript? A) Cross-Site Scripting (XSS) B) Cross-Site Request Forgery (CSRF) C) Buffer overflow D) SQL injection Answer: A Explanation: Unsanitized user input can lead to XSS attacks, where malicious scripts are injected into web pages and executed in other users' browsers.
Developer Expert Exam
B) Jest C) Selenium D) Mocha Answer: B Explanation: Jest is a popular JavaScript testing framework that provides an easy-to-use API for unit testing components in Adobe Commerce. Question 13. Which RequireJS configuration property specifies the path for a module? A) shim B) paths C) deps D) config
Developer Expert Exam
Answer: B Explanation: The paths property in RequireJS configuration defines the module's URL or path for dependency management. Question 14. How does jQuery integrate with Magento's frontend? A) Via direct DOM manipulation and event handling B) Through custom PHP scripts C) By replacing RequireJS D) Using server-side rendering only Answer: A Explanation: jQuery is used extensively for DOM manipulation, event handling, and AJAX calls in Magento's frontend.
Developer Expert Exam
B) JS
C) PHTML
D) JSON
Answer: A Explanation: UI Components are primarily defined in XML layout files, specifying structure, data sources, and configuration. Question 17. In Knockout.js, what is an observable? A) A variable that stores static data B) A function that updates the DOM automatically when data changes C) A function that reacts to events only D) A method for AJAX calls
Developer Expert Exam
Answer: B Explanation: Observables are special variables in Knockout.js that notify the UI to update automatically when their values change. Question 18. Which Knockout.js feature allows combining multiple observables into a derived value? A) Observable B) Computed observable C) Binding D) Template Answer: B Explanation: Computed observables derive their value from other observables and automatically update when dependencies change.
Developer Expert Exam
A) To define global variables B) To initialize JavaScript components with configuration data C) To include CSS styles D) To load external scripts asynchronously Answer: B Explanation: data-mage-init initializes Magento UI components via JavaScript, passing configuration options inline in HTML. Question 21. Which global JavaScript object contains the configuration data for the checkout process? A) window.customerData B) window.checkoutConfig C) window.dataProvider
Developer Expert Exam
D) window.uiComponent Answer: B Explanation: window.checkoutConfig holds configuration data for the checkout, including payment and shipping options. Question 22. Which technique is used to override or extend existing JavaScript components in Magento 2? A) Using mixins B) Editing core files directly C) Disabling RequireJS D) Replacing PHP controllers only Answer: A
Developer Expert Exam
Question 24. How can you customize the checkout architecture in Adobe Commerce? A) By editing core PHP files only B) By creating or overriding Knockout.js components and JavaScript modules C) By modifying only layout XML files D) By changing database schemas directly Answer: B Explanation: Customizations involve creating or overriding Knockout.js components, JavaScript modules, and interacting with checkout API. Question 25. Which client-side validation approach is most effective during checkout? A) Server-side validation only
Developer Expert Exam
B) JavaScript validation using Knockout.js and custom scripts before submission C) Disabling all validation D) Relying solely on HTML5 validation attributes Answer: B Explanation: JavaScript validation provides immediate feedback and prevents submission of invalid data during checkout. Question 26. What is the purpose of customer data sections (CustomerData) in Magento? A) To store server-side user sessions only B) To manage client-side data that persists across checkout steps and is dynamically updated
