Array Iterators

Question 1

Returns an iterator that contains key/value pairs of each index in the array

Answer 1

array.entries()

Question 2

Tests whether all elements in the array pass the test implemented by the provided function

Answer 2

array.every()

Question 3

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

Answer 3

array.filter() (immutable - creates a new array)

Question 4

Returns the first element in an array that satisfies the provided testing function.

Answer 4

array.find()

Question 5

Return the index of the first element in an array that satisfies the provided testing function.

Answer 5

array.findIndex()

Question 6

Iterates the array in reverse order and returns the value of the first element that satisfies the provided testing function.

Answer 6

array.findLast()

Question 7

Iterates the array in reverse order and returns the index of the first element that satisfies the provided testing function.

Answer 7

array.findLastIndex()

Question 8

Apply callback and flatten results 1 level

Answer 8

array.flatMap()

const arr1 = [1, 2, 1];

const result = arr1.flatMap((num) => (num === 2 ? [2, 2] : 1));
// Expected output: Array [1, 2, 2, 1]

Question 9

Execute a provided function once for each array element.

Answer 9

array.forEach()

Question 10

When you want to transform elements in an array.

Answer 10

array.map()

Question 11

When you want derive a single value from multiple elements in an array.

Answer 11

array.reduce()

Question 12

Derive a single value from multiple elements in an array from right to left.

Answer 12

array.reduceRight()

Question 13

Test that at least one element of the array passes the test implemented by the given function

Answer 13

array.some()