JavaScript

Question 1

Describe scope in Javascript?

Answer 1

In javascript, there are two kinds of scope. Global scope and function scope. If the variable definition happens inside of a function the variable is defined with function local scoped. Otherwise, the variable is defined with a global scope meaning it’s created as a member of a global object

Question 2

What is hoisting?

Answer 2

Hoisting is when the javascript interpreter assigns variable declarations a value of undefined when it’s evaluating the code.

Question 3

What is the difference between let and var?

Answer 3

var is function scoped and when accessed before initialized returns undefined. let is block scoped and returns a reference error when accessed before initialization.

Question 4

what’s the difference between const and let?

Answer 4

const and let are both block-scoped and return reference errors when accessed before initialization. The only difference is that const cannot be reassigned, but it is mutable.

Question 5

What is an async function?

Answer 5

An async function is an asynchronous function, it always returns a promise.

Question 6

What is a promise?

Answer 6

A promise in javascript is a way to return a value in a way that is time-independent. with a promise you can specify chains of asynchronous steps, using the .then(…) method on a returned promise.

Question 7

What is a pure function?

Answer 7

A pure function takes arguments and returns values based on those arguments.

Question 8

What is an impure function?

Answer 8

Impure functions can mutate objects outside of their scope or produce side effects.