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Quiz Questions

Explain your understanding of the box model and how you would tell the browser in CSS to render your layout in different box models.
What does `* { box-sizing: border-box; }` do?
What is CSS selector specificity and how does it work?
What is the CSS `display` property and can you give a few examples of its use?
What's the difference between a `relative`, `fixed`, `absolute`, `sticky` and `static`-ally positioned element?
What's the difference between `inline` and `inline-block`?
Explain the concept of "hoisting" in JavaScript
What is React? Describe the benefits of React
What are the differences between JavaScript variables created using `let`, `var` or `const`?
What is the difference between `==` and `===` in JavaScript?
What is the event loop in JavaScript runtimes?
What is the difference between state and props in React?
Explain event delegation in JavaScript
What is the purpose of the `key` prop in React?
Explain how `this` works in JavaScript
Describe the difference between a cookie, `sessionStorage` and `localStorage` in browsers
Describe the difference between `<script>`, `<script async>` and `<script defer>`
What's the difference between a JavaScript variable that is: `null`, `undefined` or undeclared?
What are the benefits of using hooks in React?
What's the difference between `.call` and `.apply` in JavaScript?
Why is it generally a good idea to position CSS `<link>`s between `<head></head>` and JS `<script>`s just before `</body>`?
Explain how a browser determines what elements match a CSS selector.
Have you played around with the new CSS Flexbox or Grid specs?
Is there any reason you'd want to use `translate()` instead of `absolute` positioning, or vice-versa? And why?
What are the rules of React hooks?
Explain `Function.prototype.bind` in JavaScript
What advantage is there for using the JavaScript arrow syntax for a method in a constructor?
Explain how prototypal inheritance works in JavaScript
Difference between: `function Person(){}`, `const person = Person()`, and `const person = new Person()` in JavaScript?
Explain the differences on the usage of `foo` between `function foo() {}` and `var foo = function() {}` in JavaScript
What's a typical use case for anonymous functions in JavaScript?
What are the various ways to create objects in JavaScript?
What is a closure in JavaScript, and how/why would you use one?
What is the definition of a higher-order function in JavaScript?
What does re-rendering mean in React?
What are the differences between JavaScript ES2015 classes and ES5 function constructors?
Describe event bubbling in JavaScript and browsers
Describe event capturing in JavaScript and browsers
Explain the difference between synchronous and asynchronous functions in JavaScript
What are the pros and cons of using Promises instead of callbacks in JavaScript?
How would one optimize the performance of React contexts to reduce rerenders?
How do you handle asynchronous data loading in React applications?
How do you decide between using React state, context, and external state managers?
What is virtual DOM in React?
How does virtual DOM in React work? What are its benefits and downsides?
What is reconciliation in React?
What is the difference between React Node, React Element, and a React Component?
What is JSX and how does it work?
What is the consequence of using array indices as the value for `key`s in React?
What are some pitfalls about using context in React?
Describe Block Formatting Context (BFC) and how it works.
Describe `float`s and how they work.
Describe pseudo-elements and discuss what they are used for.
Describe `z-index` and how stacking context is formed.
What kind of things must you be wary of when designing or developing for multilingual sites?
Explain CSS sprites, and how you would implement them on a page or site.
Have you ever used a grid system, and if so, what do you prefer?
How do you serve a page with content in multiple languages?
How do you serve your pages for feature-constrained browsers?
How is responsive design different from adaptive design?
How would you approach fixing browser-specific styling issues?
What are `data-` attributes good for?
What are the advantages/disadvantages of using CSS preprocessors?
What are the different ways to visually hide content (and make it available only for screen readers)?
What is progressive rendering?
What's the difference between feature detection, feature inference, and using the UA string?
What's the difference between "resetting" and "normalizing" CSS?
Why you would use a `srcset` attribute in an image tag?
What does the dependency array of `useEffect` affect?
What is the `useRef` hook in React and when should it be used?
What is the `useCallback` hook in React and when should it be used?
What is the `useMemo` hook in React and when should it be used?
What is the `useReducer` hook in React and when should it be used?
What are React Fragments used for?
How do you reset a component's state in React?
What is `'use strict';` in JavaScript for?
Explain AJAX in as much detail as possible
What are React Portals used for?
What are the advantages and disadvantages of using AJAX?
What are the differences between `XMLHttpRequest` and `fetch()` in JavaScript and browsers?
How do you abort a web request using `AbortController` in JavaScript?
What are JavaScript polyfills for?
Why is extending built-in JavaScript objects not a good idea?
Why is it, in general, a good idea to leave the global JavaScript scope of a website as-is and never touch it?
What are higher order components in React?
Explain the differences between CommonJS modules and ES modules in JavaScript
What is the Flux pattern and what are its benefits?
Explain one-way data flow of React and its benefits
What are iterators and generators in JavaScript and what are they used for?
Explain the difference between mutable and immutable objects in JavaScript
Explain the presentational vs container component pattern in React
What is the difference between a `Map` object and a plain object in JavaScript?
What are the differences between `Map`/`Set` and `WeakMap`/`WeakSet` in JavaScript?
What are render props in React and what are they for?
Why might you want to create static class members in JavaScript?
What are `Symbol`s used for in JavaScript?
What are server-sent events?
Explain the composition pattern in React
What are JavaScript object property flags and descriptors?
What are JavaScript object getters and setters for?
What is React Fiber and how is it an improvement over the previous approach?
What are workers in JavaScript used for?
What is React Suspense and what does it enable?
How does JavaScript garbage collection work?
Explain what happens when `setState` is called in React
Can you offer a use case for the new arrow => function syntax?
Explain what a single page app is and how to make one SEO-friendly
What's the difference between an "attribute" and a "property" in the DOM?
What is the difference between controlled and uncontrolled React Components?
Are you familiar with styling SVG?
Can you explain the difference between coding a website to be responsive versus using a mobile-first strategy?
Can you give an example of an `@media` property other than `screen`?
Describe what you like and dislike about the CSS preprocessors you have used.
Have you ever worked with retina graphics?
Have you used or implemented media queries or mobile-specific layouts/CSS?
Consider HTML5 as an open web platform. What are the building blocks of HTML5?
What are some of the "gotchas" for writing efficient CSS?
What are the various clearing techniques and which is appropriate for what context?
What does a `DOCTYPE` do?
What existing CSS frameworks have you used locally, or in production?
Why would you use something like the `load` event?
What is the difference between `useEffect` and `useLayoutEffect` in React?
What is the purpose of callback function argument format of `setState()` in React and when should it be used?
What is the `useId` hook in React and when should it be used?
What is `forwardRef()` in React used for?
What is the difference between `mouseenter` and `mouseover` event in JavaScript and browsers?
Why does React recommend against mutating state?
What are error boundaries in React for?
How do you test React applications?
Explain what React hydration is
How do you debug React applications?
What is React strict mode and what are its benefits?
How do you localize React applications?
What is code splitting in a React application?
What are the various data types in JavaScript?
What language constructs do you use for iterating over object properties and array items in JavaScript?
What are the benefits of using spread syntax in JavaScript and how is it different from rest syntax?
Explain server-side rendering of React applications and its benefits?
Explain static generation of React applications and its benefits?
What are some common pitfalls when doing data fetching in React?
What are some React anti-patterns?
What are proxies in JavaScript used for?
What tools and techniques do you use for debugging JavaScript code?
Difference between document `load` event and document `DOMContentLoaded` event?
Explain how JSONP works (and how it's not really Ajax)
Explain the concept of a callback function in asynchronous operations
Explain the concept of a microtask queue
Explain the concept of caching and how it can be used to improve performance
Explain the concept of code coverage and how it can be used to assess test quality
Explain the concept of Content Security Policy (CSP) and how it enhances security
Explain the concept of Cross-Site Request Forgery (CSRF) and its mitigation techniques
Explain the concept of debouncing and throttling
Explain the concept of destructuring assignment for objects and arrays
Explain the concept of error propagation in JavaScript
Explain the concept of hoisting with regards to functions
Explain the concept of inheritance in ES2015 classes
Explain the concept of input validation and its importance in security
Explain the concept of lazy loading and how it can improve performance
Explain the concept of lexical scoping
Explain the concept of partial application
Explain the concept of scope in JavaScript
Explain the concept of tagged templates
Explain the concept of test-driven development (TDD)
Explain the concept of the Prototype pattern
Explain the concept of the Singleton pattern
Explain the concept of the spread operator and its uses
Explain the concept of the Strategy pattern
Explain the concept of the Web Socket API
Explain the concept of `this` binding in event handlers
Explain the concept of tree shaking in module bundling
Explain the difference between classical inheritance and prototypal inheritance
Explain the difference between `document.querySelector()` and `document.getElementById()`
Explain the difference between dot notation and bracket notation for accessing object properties
Explain the difference between global scope, function scope, and block scope
Explain the difference between shallow copy and deep copy
Explain the difference between unit testing, integration testing, and end-to-end testing
Explain the difference in hoisting between `var`, `let`, and `const`
Explain the different states of a Promise
Explain the different ways the `this` keyword can be bound
Explain the event phases in a browser
Explain the Observer pattern and its use cases
Explain the same-origin policy with regards to JavaScript
Explain why the following doesn't work as an IIFE: `function foo(){}();`. What needs to be changed to properly make it an IIFE?
How can closures be used to create private variables?
How can you avoid problems related to hoisting?
How can you create custom error objects?
How can you implement secure authentication and authorization in JavaScript applications?
How can you optimize DOM manipulation for better performance?
How can you optimize network requests for better performance?
How can you prevent clickjacking attacks?
How can you prevent SQL injection vulnerabilities in JavaScript applications?
How can you share code between JavaScript files?
How can you test asynchronous code in JavaScript?
How do currying and partial application differ from each other?
How do `<iframe>` on a page communicate?
How do `Set`s and `Map`s handle equality checks for objects?
How do you access the index of an element in an array during iteration?
How do you add, remove, and modify HTML elements using JavaScript?
How do you add, remove, and update elements in an array?
How do you check if an object has a specific property?
How do you check the data type of a variable?
How do you convert a `Set` to an array in JavaScript?
How do you convert a string to a number in JavaScript?
How do you create a constructor function?
How do you detect if JavaScript is disabled on a page?
How do you get the query string values of the current page in JavaScript?
How do you handle errors in asynchronous operations?
How do you handle errors using `try...catch` blocks?
How do you import and export modules in JavaScript?
How do you make an HTTP request using the Fetch API?
How do you manipulate CSS styles using JavaScript?
How do you organize your code?
How do you prevent the default behavior of an event?
How do you redirect to a new page in JavaScript?
How do you reliably determine whether an object is empty?
How do you use `window.history` API?
How do you validate form elements using the Constraint Validation API?
How do you write unit tests for JavaScript code?
How does hoisting affect function declarations and expressions?
How is `Promise.all()` different from `Promise.allSettled()`?
Provide some examples of how currying and partial application can be used
What are callback functions and how are they used?
What are default parameters and how are they used?
What are design patterns and why are they useful?
What are event listeners and how are they used?
What are mocks and stubs and how are they used in testing?
What are modules and why are they useful?
What are Progressive Web Applications (PWAs)?
What are Promises and how do they work?
What are rest parameters and how are they used?
What are `Set`s and `Map`s and how are they used?
What are some best practices for handling sensitive data in JavaScript?
What are some best practices for writing maintainable and effective tests in JavaScript?
What are some common performance bottlenecks in JavaScript applications?
What are some common security headers and their purpose?
What are some of the advantages/disadvantages of writing JavaScript code in a language that compiles to JavaScript?
What are some popular JavaScript testing frameworks?
What are some techniques for reducing reflows and repaints?
What are some tools and techniques for identifying security vulnerabilities in JavaScript code?
What are some tools that can be used for JavaScript testing?
What are some tools that can be used to measure and analyze JavaScript performance?
What are template literals and how are they used?
What are the advantages of using the spread operator with arrays and objects?
What are the benefits of using a module bundler?
What are the benefits of using currying and partial application?
What are the common pitfalls of using the `this` keyword?
What are the different methods for iterating over an array?
What are the different types of errors in JavaScript?
What are the different types of testing in software development?
What are the different ways to copy an object or an array?
What are the different ways to make an API call in JavaScript?
What are the metadata fields of a module?
What are the potential issues caused by hoisting?
What are the potential pitfalls of using closures?
What are Web Workers and how can they be used to improve performance?
What do you think of AMD vs CommonJS?
What is async/await and how does it simplify asynchronous code?
What is Cross-Site Scripting (XSS) and how can you prevent it?
What is currying and how does it work?
What is `Object.freeze()` for?
What is `Object.preventExtensions()` for?
What is `Object.seal()` for?
What is recursion and how is it used in JavaScript?
What is the Command pattern and how is it used?
What is the Decorator pattern and how is it used?
What is the difference between a parameter and an argument?
What is the difference between `event.preventDefault()` and `event.stopPropagation()`?
What is the difference between `innerHTML` and `textContent`?
What is the difference between `setTimeout()`, `setImmediate()`, and `process.nextTick()`?
What is the difference between the Window object and the Document object?
What is the DOM and how is it structured?
What is the Factory pattern and how is it used?
What is the `Intl` namespace object for?
What is the Module pattern and how does it help with encapsulation?
What is the prototype chain and how does it work?
What is the purpose of the `break` and `continue` statements?
What is the purpose of the `finally` block?
What is the purpose of the `new` keyword?
What is the purpose of the `switch` statement?
What is the spread operator and how is it used?
What is the ternary operator and how is it used?
What is the use of `Promise.all()`
When would you use `document.write()`?

Quiz

What is the difference between `useEffect` and `useLayoutEffect` in React?

Topics

React

←Previous Why would you use something like the `load` event?

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