Question: What is the difference between `==` and `===` in JavaScript?
Answer: `==` is the equality operator, which checks for equality after performing necessary type conversions. For example, `2 == “2” would return `true` because the string `2’` is converted to the number `2` before comparison.
`===` is the strict equality operator, which checks for equality without type conversion. For example, `2 === ‘2` would return `false` because the operands are of different types.
Question: What is a closure in JavaScript?
Answer:A closure is a function that has access to its own scope, the scope of the outer function, and the global scope. This means that a function defined inside another function can remember the variables from the outer function’s scope, even after the outer function has finished executing. Closures are often used for data privacy and to create function factories.
Example:
javascript
function outer() {
let counter = 0;
return function inner() {
counter++;
console.log(counter);
};
}
const increment = outer();
increment(); // 1
increment(); // 2
Question: Explain the concept of Responsive Web Designing.
Answer: Responsive design is an approach to web design that ensures web pages render well on a variety of devices like desktop, tablet, or mobile phone.
and window or screen sizes. This is achieved using flexbox, grids, and CSS media queries.
Question: What is the purpose of the `DOCTYPE` declaration in HTML?
Answer: The `DOCTYPE` declaration is used to specify the HTML version and type of document. It helps the browser understand how to render the page correctly. For example, `<!DOCTYPE html>` declares that the document is an HTML5 document. It helps ensure that the web page is rendered in standards mode
Question: Can you explain the box model in CSS?
Answer:
The CSS box model describes the rectangular boxes that are generated for elements in the document tree and consists of four components:
- Content: The content of the box, where text and images appear.
- Padding: The space between the content and the border. It is inside the box and transparent.
- Border: A border surrounding the padding (if any) and content.
- Margin: The space outside the border, separating the element from other elements.
Understanding the box model is crucial for designing layouts and controlling spacing around elements.
Question: What is the difference between id and class attributes in HTML?
Answer: The id and class attributes in HTML are used to assign styles and scripts to elements, but they serve different purposes:
- id:
- The id attribute is used to uniquely identify a single element on a page. It must be unique within the document, meaning no two elements can have the same id.
- It is useful for targeting a specific element with CSS or JavaScript.
Example:
<div id=”header”>This is the header</div>
- class:
- The class attribute can be used on multiple elements to group them together. Multiple elements can share the same class name.
- It is useful for applying styles or JavaScript behaviours to multiple elements at once.
Example:
<div class=”button”>Button 1</div>
<div class=”button”>Button 2</div>
In CSS, you target id attributes using the # symbol and class attributes using the . symbol. For example, “#header” selects the element with the id of “header,” while “.button” selects all elements with the class “button.”
Question: What is CSS?
Answer: CSS (Cascading Style Sheets) is a stylesheet language used to describe the presentation of a document written in HTML or XML. CSS controls the layout, colours, fonts, and overall visual appearance of web pages, allowing developers to create visually engaging and consistent designs across different pages.
Question: What is the difference between `let`, `var`, and `const` in JavaScript?
Answer:
- var: Function-scoped or globally-scoped. Variables declared with `var` can be redeclared and updated.
- `let`: Block-scoped. Variables declared with `let` can be updated but not redeclared in the same scope.
- `const`: Block-scoped. Variables declared with `const` cannot be updated or redeclared.
Question: What is the difference between block-level , inline elements and inline-block in HTML?
Answer:
- Block-level elements: Take up the full width available, and start on a new line. Examples include `<div>`, `<h1>` to `<h6>`, `<p>`, `<header>`
- Inline elements: Only take up as much width as necessary and do not start on a new line also width and height is not applicable. Examples include `<span>`, `<a>`, `<img>`
- Inline-block elements : It has properties of both inline and block elements. It inlines the next elements in the same line and also applies width and height to the elements.
Examples : <button> , <input>
Question: What is HTML?
Answer: HTML (HyperText Markup Language) is the standard language used to create and structure content on the web. It consists of a series of elements represented by tags that define different parts of the web page, such as headings, paragraphs, links, images, and other multimedia elements.
Question: What is the Document Object Model (DOM)?
Answer: The Document Object Model (DOM) is a programming interface for web documents. It represents the page as a tree structure where each node is an object representing a part of the document. JavaScript can interact with the DOM to dynamically update content, structure, and styles of a web page in response to user actions.
Question: What is React and why is it popular in web development?
Answer: React is a JavaScript library for building user interfaces, particularly single-page applications where you need a fast and interactive user experience. Developed by Facebook, it allows developers to create reusable UI components. React is popular because it makes it easier to build complex, dynamic web applications efficiently and improves performance with its virtual DOM.
Question: What are React components?
Answer: React components are the building blocks of a React application. They are self-contained pieces of the user interface that can be reused throughout the application. Components can be functional (using functions) or class-based (using ES6 classes). Functional components are typically used with React Hooks for managing state and side effects.
Question: What are React Hooks, and why are they useful?
Answer: A Hook in React is a special function, hooks are a feature in React that allows you to use state and other React features in functional components. The primary hooks, such as `useState` and `useEffect`, enable state management and side effects handling. Hooks promote cleaner and more concise code by reducing the need for class components and allowing for better separation of concerns. They make it easier to reuse logic across multiple components, leading to more maintainable and scalable applications.
Question: What is JSX in React?
Answer: JSX (JavaScript XML) is a syntax extension for JavaScript that looks similar to HTML. It is used in React to describe the UI structure within JavaScript code. JSX makes it easier to write and visualise the component structure by combining HTML and JavaScript in the same file. During the build process, JSX is transformed into standard JavaScript function calls.
