JS Arrays

Question 1

What are arrays used for?

Answer 1

To store a list of data/values

Question 2

Describe array literal notation.

Answer 2

Array literal notation is square brackets [ ]. Within the square brackets, values are nested inside. Each are separated by a comma.

Question 3

How are arrays different from “plain” objects?

Answer 3

There is an actual order to it the values of the array. Arrays have indexes.

Question 4

What number represents the first index of an array?

Answer 4

0 (zero)

Question 5

What is the length property of an array?

Answer 5

The number of indexes in the array — (how many entries are in the array).

Question 6

How do you calculate the last index of an array?

Answer 6

array[lastIndex] = array.length - 1

Question 7

What isArray.prototype.filteruseful for?

Answer 7

To filter out arrays

Creates a new array with all elements that pass the test implemented by the provided function.

Question 8

What isArray.prototype.mapuseful for?

Answer 8

Every element of array

Creates a new array populated with the results of calling a provided function on every element in the calling array.

Question 9

What isArray.prototype.reduceuseful for?

Answer 9

To reduce an array into a singular value

Executes a reducer function (that you provide) on each element of the array, resulting in a single output value.