Front End Developer Interview Questions Every Developer Should Know

1. What is HTML, and why is it important in web development?
HTML (HyperText Markup Language) structures web content and is the backbone of web pages. It organizes elements like headings, paragraphs, and links, enabling browsers to render content for users.

2. Can you explain the difference between HTML, CSS, and JavaScript?

HTML: Structures the content of a web page.
CSS: Styles the appearance of the content (e.g., colors, layouts).
JavaScript: Adds interactivity and dynamic functionality to web pages.

3. What is semantic HTML, and why is it important?
Semantic HTML uses meaningful tags (e.g., <header>, <article>, <footer>) that describe the purpose of the content. This improves accessibility, SEO, and code readability.

4. What is the difference between id and class in HTML?

id: A unique identifier for a single element.
class: Can be applied to multiple elements for grouping and styling.

5. What are CSS selectors, and can you name a few?
CSS selectors define elements to which styles are applied. Examples:

Universal: *
Class: .classname
ID: #idname
Element: div, p
Attribute: [type="text"]

6. What is the difference between inline, internal, and external CSS?

Inline CSS: Applied directly within an element’s style attribute.
Internal CSS: Defined within a <style> block in the <head>.
External CSS: Linked using an external file via <link>.

7. Can you explain the Box Model in CSS?
The Box Model consists of:

Content: The actual content area.
Padding: Space between content and border.
Border: Encases padding and content.
Margin: Space between the border and other elements.

8. What is the difference between relative, absolute, and fixed positioning in CSS?

Relative: Positions an element relative to its normal position.
Absolute: Positions an element relative to its nearest positioned ancestor.
Fixed: Positions an element relative to the viewport.

9. What is responsive design, and how is it achieved?
Responsive design ensures a website looks good on all devices and screen sizes. It can be achieved using:

Media queries
Fluid grids
Flexible images

10. What are some JavaScript data types?
JavaScript has:

Primitive types: String, Number, Boolean, Undefined, Null, Symbol, BigInt
Non-primitive types: Objects and Arrays

11. What is the DOM?
The Document Object Model (DOM) is a programming interface that represents a web page as a tree structure. Developers can use JavaScript to manipulate its elements dynamically.

12. What is the difference between == and === in JavaScript?

==: Compares values after type conversion (loose equality).
===: Compares both value and type (strict equality).

13. Can you explain event delegation in JavaScript?
Event delegation allows you to handle events at a higher level, like on a parent element, to manage child elements dynamically using event bubbling.

14. What are some commonly used JavaScript frameworks or libraries for front-end development?