Javascript Array Functions

Question 1

Array.prototype.at()

Answer 1

Returns the array item at the given index. Accepts negative integers, which count back from the last item.

Question 2

Array.prototype.concat()

Answer 2

Returns a new array that is this array joined with other array(s) and/or value(s).

Question 3

Array.prototype.copyWithin()

Answer 3

Copies a sequence of array elements within the array.

Question 4

Array.prototype.entries()

Answer 4

Returns a new Array Iterator object that contains the key/value pairs for each index in the array.

Question 5

Array.prototype.every()

Answer 5

Returns true if every element in this array satisfies the testing function.

Question 6

Array.prototype.fill()

Answer 6

Fills all the elements of an array from a start index to an end index with a static value.

Question 7

Array.prototype.filter()

Answer 7

Returns a new array containing all elements of the calling array for which the provided filtering function returns true.

Question 8

Array.prototype.find()

Answer 8

Returns the FIRST found element in the array, if some element in the array satisfies the testing function, or undefined if not found.

Question 9

Array.prototype.findIndex()

Answer 9

Returns the found index in the array, if an element in the array satisfies the testing function, or -1 if not found.

Question 10

Array.prototype.forEach()

Answer 10

Calls a function for each element in the array.

Question 11

Array.prototype.includes()

Answer 11

Determines whether the array contains a value, returning true or false as appropriate.

Question 12

Array.prototype.indexOf()

Answer 12

Returns the first (least) index of an element within the array equal to an element, or -1 if none is found.

Question 13

Array.prototype.join()

Answer 13

Joins all elements of an array into a string.

Question 14

Array.prototype.keys()

Answer 14

Returns a new Array Iterator that contains the keys for each index in the array.

Question 15

Array.prototype.lastIndexOf()

Answer 15

Returns the last (greatest) index of an element within the array equal to an element, or -1 if none is found.

Question 16

Array.prototype.map()

Answer 16

Returns a new array containing the results of calling a function on every element in this array.

Question 17

Array.prototype.pop()

Answer 17

Removes the last element from an array and returns that element.

Question 18

Array.prototype.push()

Answer 18

Adds one or more elements to the end of an array, and returns the new length of the array.

Question 19

Array.prototype.reduce()

Answer 19

Apply a function against an accumulator and each value of the array (from left-to-right) as to reduce it to a single value.

Question 20

Array.prototype.reduceRight()

Answer 20

Apply a function against an accumulator> and each value of the array (from right-to-left) as to reduce it to a single value.

Question 21

Array.prototype.reverse()

Answer 21

Reverses the order of the elements of an array in place. (First becomes the last, last becomes first.)

Question 22

Array.prototype.shift()

Answer 22

Removes the first element from an array and returns that element.

Question 23

Array.prototype.slice()

Answer 23

Extracts a section of the calling array and returns a new array.

Question 24

Array.prototype.some()

Answer 24

Returns true if at least one element in this array satisfies the provided testing function.

Question 25

Array.prototype.sort()

Answer 25

Sorts the elements of an array in place and returns the array.

Question 26

Array.prototype.splice()

Answer 26

Adds and/or removes elements from an array.

Question 27

Array.prototype.unshift()

Answer 27

Adds one or more elements to the front of an array, and returns the new length of the array.

Question 28

Array.prototype.values()

Answer 28

Returns a new Array Iterator object that contains the values for each index in the array.