JavaScript 2 CSS 1

JavaScript 188 Node 51 CSS 15 React 12 HTML 11 Accessibility 9 Contributing 7

What is the difference between the array methods `map()` and `forEach()`? 60 How can you avoid callback hells? 50 What is short-circuit evaluation in JavaScript? 38 Explain the differences between imperative and declarative programming. 37 What is ARIA and when should you use it? 4 What is the difference between an element and a component in React? 4 Describe the layout of the CSS Box Model and briefly describe each component. 3 What is a closure? Can you give a useful example of one? 2 How do you clone an object in JavaScript? 2 What is the difference between `null` and `undefined`? 2 NodeJS often uses a callback pattern where if an error is encountered during execution, this error is passed as the first argument to the callback. What are the advantages of this pattern? 2 What is functional programming? 2 What does `0.1 + 0.2 === 0.3` evaluate to? 2 What is event-driven programming? 2 What is WCAG? What are the differences between A, AA, and AAA compliance? 2 What is a stateful component in React? 2 What are the advantages of using CSS sprites and how are they utilized? 2 What are JavaScript data types? 2 Can you name the four types of `@media` properties? 2 How do you compare two objects in JavaScript? 2 What is the difference between '+' and '~' sibling selectors?. 2 How does hoisting work in JavaScript? 2 What are landmark roles and how can they be useful? 2 What are truthy and falsy values in JavaScript? 2 What is the purpose of JavaScript UI libraries/frameworks like React, Vue, Angular, Hyperapp, etc? 1 What is CSS BEM? 1 What is the difference between an expression and a statement in JavaScript? 1 Generate an array, containing the Fibonacci sequence, up until the nth term. 1 What is the difference between HTML and React event handling? 1 What is the difference between lexical scoping and dynamic scoping? 1 Discuss the differences between an HTML specification and a browser’s implementation thereof. 1 What is CORS? 1 What is a pure function? 1 What is the DOM? 1 What are portals in React? 1 What is the difference between the equality operators `==` and `===`? 1 What is event delegation and why is it useful? Can you show an example of how to use it? 1 Explain the difference between a static method and an instance method. 1 What is the `this` keyword and how does it work? 1 What does the following function return? 1 What is the `children` prop? 1 What is a focus ring? What is the correct solution to handle them? 1 What is the purpose of callback function as an argument of `setState`? 1 What is a virtual DOM and why is it used in libraries/frameworks? 1 What are fragments? 1 Create a function `pipe` that performs left-to-right function composition by returning a function that accepts one argument. 1 In which states can a Promise be? 1 What are Promises? 1 What are `defer` and `async` attributes on a `<script>` tag? 1 What is the event loop in Node.js? 1 What is the purpose of the `alt` attribute on images? 1 What are inline conditional expressions? 1 What is a callback? Can you show an example using one? 1 Contrast mutable and immutable values, and mutating vs non-mutating methods. 1 What is the difference between `em` and `rem` units? 1 What are the advantages of using CSS preprocessors? 1 What are some differences that XHTML has compared to HTML? 1 Can you describe how CSS specificity works? 1 What is memoization? 1 What is a cross-site scripting attack (XSS) and how do you prevent it? 1 What is a key? What are the benefits of using it in lists? 1 What is the purpose of cache busting and how can you achieve it? 1 How do you ensure methods have the correct `this` context in React component classes? 1 What is the Accessibility Tree? 1 What is Big O Notation? 1 What does `'use strict'` do and what are some of the key benefits to using it? 1 Using flexbox, create a 3-column layout where each column takes up a `col-{n} / 12` ratio of the container. 1 How does prototypal inheritance differ from classical inheritance? 1 What is HTML5 Web Storage? Explain `localStorage` and `sessionStorage`. 1 Briefly describe the correct usage of the following HTML5 semantic elements: `<header>`, `<article>`,`<section>`, `<footer>` 1 Where and why is the `rel="noopener"` attribute used? 1 What is the output of the following code? 1 What is the only value not equal to itself in JavaScript? 1 What is context? 1 What are the differences between `var`, `let`, `const` and no keyword statements? 1 What are refs in React? When should they be used? 1 What is a MIME type and what is it used for? 1 Can a web page contain multiple `<header>` elements? What about `<footer>` elements? 1 What does the following code evaluate to? 1 What is recursion and when is it useful? 1

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