- What are
data-
attributes good for? - Describe the difference between
<script>
,<script async>
and<script defer>
on page loading. - Why is it generally a good idea to position CSS
<link>
s between<head></head>
and JS<script>
s just before</body>
? Do you know any exceptions? - Why you would use a
srcset
attribute in an image tag? Explain the process the browser uses when evaluating the content of this attribute. - What is the difference between
canvas
andsvg
? - What is progressive rendering?
- Describe z-index and how stacking context is formed.
- What are the different ways to visually hide content ? How would you make sure to have hidden content accessible (for visual disabilities) ?
- What is CSS selector specificity and how does it work?
- Describe pseudo-elements and discuss what they are used for.
- 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 happens when you use
display:
inline-block
,inline-flex
orinline-grid
instead ofblock
,flex
orgrid
? - What's the difference between the "nth-of-type()" and "nth-child()" selectors?
- What's the difference between a relative, fixed, absolute and statically positioned element?
- What existing CSS frameworks have you used locally, or in production? How would you change/improve them?
- Is there any reason you'd want to use
translate()
instead of absolute positioning, or vice-versa? And why? - Can you explain the difference between px, em and rem as they relate to font sizing?
- Can you give an example of a pseudo class? Can you provide an example use case for a pseudo class?
- What is the difference between CSS Grid and Flexbox? When would you use one over the other?
- Describe BFC (Block Formatting Context) and how it works.
- What's the difference between a variable that is:
null
,undefined
or undeclared?- How would you go about checking for any of these states?
- What is a closure, and how/why would you use one?
- What language syntax or built-in functions do you use for iterating over object properties and array items?
- Can you describe the main difference between the
Array.forEach()
andArray.map()
methods and why you would pick one versus the other? - What's a typical use case for anonymous functions?
- What is the difference between
==
and===
? - Explain the same-origin policy with regards to JavaScript.
- Explain the difference between mutable and immutable objects.
- What is an example of an immutable object in JavaScript?
- What are the pros and cons of immutability?
- How can you achieve immutability in your own code?
- Explain the difference between synchronous and asynchronous functions.
- What are the differences between variables created using
let
,var
orconst
? - What is the definition of a higher-order function?
- Can you give an example for destructuring an object or an array?
- What are the benefits of using
spread syntax
and how is it different fromrest syntax
? - What happens if you add
async
to a function declaration?- When would you use this
async
modifier?
- When would you use this
- What is a promise? Where and how would you use promise?
- [advanced] Can you give an example of a curry function and why this syntax offers an advantage?
- Describe event bubbling.
- Describe event capturing.
- Explain how
this
works in JavaScript.- Can you give an example of one of the ways that working with
this
has changed in ES6?
- Can you give an example of one of the ways that working with
- Explain how prototypal inheritance works.
- What advantage is there for using the arrow syntax for a property value instead of a method definition ?
-
What is state in React?
-
What are props in React?
-
What is the difference between state and props?
-
[Hooks] when using
React.useState()
why would you use a function as parameter ? -
[Hooks] when using state (e.g.
const [updated, setUpdated] = React.useState()
) what happens when you use a function as parameter tosetUpdated()
? -
What are inline conditional expressions?
-
What is "key" prop and what is the benefit of using it in arrays of elements?
-
What is the use of refs?
-
How to create refs?
-
[Advanced] What are forward refs?
-
What is Virtual DOM?
-
[Advanced] What is the difference between Shadow DOM and Virtual DOM?
-
What is the difference between createElement and cloneElement?
-
[Hooks] How is used the return value of a
React.useEffect()
callback function? -
What is context?
-
What is children prop?
-
what is the difference between an array and a map?