Architecture Studio · Concepts
Conceptual Questions
Build the mental models behind frontend decisions: browser engines, runtime behavior, Web APIs, rendering, and modern UI architecture.
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244 questionsAbortController — cancelling async work the right wayMediumAdding, removing, and mutating DOM elements in vanilla JSMediumWhat AJAX actually means todayMediumAnonymous functions — what they are and where they shineMediumaria-label, aria-labelledby, and aria-live in practiceMediumWhy array indices make bad React keysMediumasync/await — syntactic sugar over promisesHardHow to test asynchronous code without flaky testsMediumWhat are common async data loading patterns in React?EasyWhat is the difference between async and defer in JavaScript?MediumAttribute vs property in the DOMMediumWhat is the Beacon API?MediumWhat are the benefits of using hooks in React?EasyWhat is a Block Formatting Context?HardWhat does box-sizing: border-box mean?MediumHow does the box model work in CSS?MediumWhat is the purpose of break and continue?EasyHow do you handle browser-specific styling issues?MediumHow does caching improve performance?MediumWhat is the difference between call( ) and apply( )?MediumWhat is the difference between call( ) and bind( )?MediumWhat are callback functions?EasyExplain few methods to center elements in webpages?MediumHow do you check the data type of a variable?MediumHow do you reliably check if an object is empty?MediumHow do you check if an object has a property?MediumWhat is a static method in a class?EasyClassical vs prototypal inheritanceEasyWhat are CSS clearing techniques?MediumWhat is clickjacking and how do you prevent it?MediumWhat is the difference between Client side rendering and Server side rendering?MediumUsing closures for private variablesEasyWhat is code coverage?HardHow do you organize code in a JavaScript project?EasyWhat is Code Splitting?MediumWhat is the command pattern?EasyWhat are common data fetching pitfalls in React?HardCommon 'this' pitfallsMediumCommonJS vs ES ModulesMediumWhat are the pros and cons of compiling to JavaScript?HardExplain the composition pattern in ReactEasyWhat is the Constraint Validation API?MediumWhat is content security policy (CSP)?MediumWhat is the difference between controlled and uncontrolled components in React?EasyWhat is Cross-Origin Resource Sharing (CORS)?EasyWhat is Cross-Site Scripting (XSS)?MediumWhat is CSRF?EasyWhat is the CSS display property and what are examples of its use?MediumWhat CSS frameworks have you used?HardHow do you use CSS Grid?MediumWhere should CSS links and JS scripts be placed in HTML?MediumHow does positioning work in CSS?MediumWhat are the pros and cons of CSS preprocessors?HardWhat do you like and dislike about CSS preprocessors?HardWhat is CSS selector specificity and how does it work?HardWhat are CSS sprites?MediumWhat is currying in JavaScript?EasyWhat is the difference between currying and partial application?MediumWhat is dangerouslySetInnerHTML and why is it dangerous?MediumWhat are data attributes in HTML?EasyWhat data structure is used to represent the DOM?EasyWhat is the difference between debouncing and throttling?EasyHow do you debug React applications?MediumWhat is the decorator pattern?EasyWhat are default parameters?Mediumdefault vs named exportMediumWhat are design patterns?MediumWhat is destructuring assignment?MediumHow do you detect if JavaScript is disabled?EasyWhat is difference between a map object and a plain object in JavaScript?MediumGlobal Scope, Function Scope, and Block ScopeHardWhat is doctype in HTML in start of HTML file?MediumWhy is document.write() considered bad practice?HardHow do you optimize DOM manipulation?MediumWhat is the DOM structure?EasyWhat is the difference between dot notation and bracket notation?EasyWhat is the difference between == and === in JavaScript?MediumWhat are common CSS efficiency gotchas?EasyWhat are error boundaries in React?EasyError handling with try...catchHardHow does error propagation work in JavaScript?MediumHow do you handle errors in asynchronous operations?MediumWhat are ES2015 classes and how do they differ from ES5 function constructors?HardDescribe event capturing in JavaScriptMediumWhat is event delegation in JavaScript?MediumWhat is the event loop in JavaScript?MediumWhat is the factory pattern?EasyWhat is feature detection?EasyWhat is the difference between Flexbox and Grid?HardHow do floats work in CSS?MediumWhat is the Flux pattern?EasyWhat is forwardRef() in React?HardWhy are functions first-class objects?MediumGarbage CollectionMediumHow do you get query string values in JavaScript?MediumWhat is a higher order function?MediumHoisting pitfalls and how to avoid themMediumHow do you create a constructor function?EasyHow to improve website performance?MediumHow to prevent the UI from blocking during a long running task?MediumHow would you style an SVG?EasyWhat are the building blocks of HTML5?MediumWhat are the HTTP methods?MediumHow do iframes communicate with the parent page?MediumHow would you handle image failures in production?MediumHow would you implement dark mode and light mode?EasyHow do you import and export modules?MediumWhat is the difference between inline, inline-block, and block in CSS?MediuminnerHTML vs textContentMediumWhat is Inversion of Control?MediumWhat are the different ways to iterate over arrays?MediumHow do you iterate over object properties?MediumWhat are iterators and generators in JavaScript?EasyJavaScript data typesEasyWhat are JavaScript modules?HardWhat is JSONP?MediumWhat is JSX and how does it work?MediumWhat is the Key Prop in React?EasyHow does lazy loading improve performance?EasyCan we pass function to initial state? What is difference between passing value and passing function?EasyHow do you identify performance bottlenecks?MediumWhat tools do you use to measure performance?MediumExplain the presentational vs container component patternEasyWhat is difference between preventDefault() and stopPropagation()?MediumWhat are primitive values and reference values in JavaScript?MediumWhat is progressive rendering?MediumWhat are Progressive Web Apps?MediumPromises vs callbacksEasyWhat is prototypal inheritance?EasyHow does the prototype chain work?MediumWhat is the prototype pattern?EasyWhat are Proxies in JavaScript?MediumWhat are pseudo-elements in CSS?MediumquerySelector vs getElementByIdHardHow does re-rendering work in React?HardWhat are some common React anti-patterns?EasyWhat are the common pitfalls of React context?HardWhat is React Fiber?MediumWhat are React Fragments used for?EasyWhat is React hydration?HardWhat is the difference between React Node, React Element, and React Component?MediumWhat are React Portals?MediumHow do you decide between React state, context, and external state managers?EasyWhat is React strict mode?MediumWhat is React Suspense?MediumWhat is recursion in JavaScript?EasyHow do you redirect to a new page in JavaScript?EasyReference vs Syntax ErrorMediumWhat are reflows and repaints?HardWhat are render props in React?EasyHow do you reset a component state in React?HardWhat is the difference between Reset and Normalize CSS?MediumWhat is the difference between responsive and adaptive design?MediumRest parameters in JavaScriptMediumHow do you serve retina graphics?EasyWhat are the rules of React hooks?EasyWhat is the same-origin policy?MediumScoping GenericsMediumHow do you implement secure authentication and authorization?MediumWhat are security headers?MediumWhat tools help find security vulnerabilities?EasyWhat is semantic HTML and why does it matter for accessibility?MediumWhat are best practices for handling sensitive data?MediumWhat are server-sent events?EasyHow does server-side rendering work in React?HardHow do you serve pages for feature-constrained browsers?MediumHow do you serve content in multiple languages?MediumsessionStorage vs localStorage vs cookiesMediumHow do you convert a Set to an Array?MediumWhy use the callback format of setState?MediumShallow copy vs deep copyEasyHow do SPAs affect SEO?MediumSpread operator in JavaScriptMediumWhat is SQL injection and how do you prevent it?EasyWhat is the srcset attribute?Mediumstate vs props in ReactMediumWhat is static generation?MediumWhat is difference between stopPropagation() and stopImmediatePropagation()?HardWhat is the strategy pattern?HardHow do you convert a string to a number in JavaScript?MediumWhat is the purpose of the switch statement?EasyWhat is a symbol type?MediumWhat is difference between sync and async function?MediumCan callbacks be synchronous?MediumWhat are tagged templates in JavaScript?HardWhat are template literals?MediumWhat is the ternary operator?EasyWhat is Test Driven Development?HardHow do you test React applications?MediumWhat testing tools do you use?MediumDifferent ways to bind 'this' in JavaScriptMedium'this' binding in event handlersMediumHow does the this keyword work in JavaScript?MediumComparing CSS translate() and absolute positioning: When to use each?EasyWhat is tree shaking?MediumHow to truncate text using CSS onlyMediumWhat does typeof operator do?MediumWhat are the different types of errors in JavaScript?MediumUnit vs integration vs end-to-end testingEasyWhat is the difference between useEffect and useLayoutEffect?MediumWhat is 'use strict' in JavaScript?MediumWhat is the useCallback hook in React?MediumHow does the useEffect dependency array work?MediumWhat is the useId hook in React?EasyWhat is the useMemo hook in React?EasyWhat is the useReducer hook in React?EasyWhat is the useRef hook in React?EasyWhat happens when the useState setter function is called in React?MediumWhat are the key differences between var, let, and const in JavaScript?EasyWhat is the Virtual DOM in React?HardHow do you visually hide content but keep it accessible to screen readers?MediumWhat are the different ways to create objects in JavaScript?EasyWhat are Web Vitals?MediumWhat does preventDefault() do?MediumWhat happens when you type a URL into a browser and hit enter?MediumWhat is a closure in JavaScript?MediumWhat is AB Testing?MediumWhat is an arrow function?MediumWhat is array destructuring?HardWhat is an async thunk?EasyWhat is callback hell?HardWhat is cookie?MediumWhat is hoisting in JavaScript?HardWhat is Immutability?MediumWhat is object destructuring?MediumWhat is Responsive Design?MediumWhat is singleton pattern?MediumWhat is Temporal Dead Zone (TDZ) in JavaScript?MediumWhat is a thunk?MediumWhere Do We Use Observer Pattern in Frontend Development?EasyWhy do we use polyfills?MediumWhy is input validation important?MediumWhy does React recommend against mutating state?HardHow does the window.history API work?MediumWindow object vs Document objectEasyWhat are workers in JavaScript?HardHow do you write good unit tests?EasyWhat is the difference between XMLHttpRequest and fetch?EasyHow do z-index and stacking contexts work?HardStreaming protocols compared: SSE vs WebSockets vs HTTP/2 Push vs chunked transferEasyAbortController and how it composes with fetch + ReadableStreamMediumTextDecoder({ stream: true }): why UTF-8 boundaries break naïve streamingMediumFrom token generation to character render: the full streaming pipelineMediumRAG: where does the frontend's responsibility start and end?Medium
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