Javascript

Question 1

Difference between var and let

Answer 1

var is not scope attached, let is scope attached

Question 2

Does Javascript supports autoconversion?

Answer 2

Yes

Question 3

“This” in a method

Answer 3

Refers to the owner scope, or to the global scope

Question 4

Style from HTML

Answer 4

document.getElementById(“id”).style.fontSize

Question 5

Class from HTML

Answer 5

document.getElementById(“id”).className

Question 6

“This” alone

Answer 6

Refers to the global scope

Question 7

“This” in an event

Answer 7

Refers to the element that receives the event

Question 8

setTimeout()

Answer 8

Receives function and delay in miliseconds. Call function after delay.

Question 9

setInterval()

Answer 9

Receives function and delay in ms. Repeat function in the said delay time.

Question 10

clearInterval()

Answer 10

Receives the id from the interval. Stops the interval.

Question 11

What does sort() by default?

Answer 11

Sorts an array alphabetical and ascending.

Question 12

How to sort numeric arrays?

Answer 12

(a, b) => a-b , this will sort ascending.

Question 13

unshift()

Answer 13

Adds new elements to the beginning of an array. Overwites the original array. Returns the new lenght of the array.

Question 14

push()

Answer 14

Adds new items to the end of an array.Overwites the original array. Returns the new lenght of the array.

Question 15

shift()

Answer 15

Removes the first item of an array. Changes the original array. Returns the shifted element.

Question 16

pop()

Answer 16

Removes the last element of an array.Changes the original array. Returns the popped element.

Question 17

delete array[0]

Answer 17

Delete values in the array leaving undefined values.

Question 18

concat()

Answer 18

Creates a new array by merging (concatenating) existing arrays. It does not change the existing arrays. It always returns a new array.

Question 19

flat()

Answer 19

Reduces the dimensionality of an array. Returns a new array.

Question 20

splice()

Answer 20

Receives position, elements to delete, and values to add. Add and remove elements from array. Chnage the original array, return an array from the deleted values.

Question 21

slice()

Answer 21

Receives start and end. Return a shallow copy of the array. Does not affect the orginal array.

Question 22

Shallow copy

Answer 22

Copy an object without appointing to the same memory at first level. But nested objects gonna be appointing to the same memory space.

Question 23

Object.assign()

Answer 23

It takes at least two objects and fusion them creating a shallow copy.

Question 24

Spread operator

Answer 24

{ …object, otherproperty: “” } creates a new shallow copy object fusioning the new properties with the introduced objects.

Question 25

Deep copy

Answer 25

creates an indepent space memory clone of the object

Question 26

How do you deep copy?

Answer 26

You can use JSON.parse to an stringify object, but functions and objects as properties will be affected. install lodash and use _.copyDeep() to a whole deep copy.

Question 27

reduce()

Answer 27

It is an iterator that receives a callback that sets accumulator and current value. It returns the final value of the accumulator.