Methods

Question 1

.forEach()

Answer 1

• Used to iterate over each element in an array and perform a specified action
• It executes a provided callback function once for each element in the array, in ascending order
• Does not return a new array

var numbers = [1, 2, 3, 4, 5];
numbers.forEach(function(number) {
console.log(number);
});

Output:
1
2
3
4
5

Question 2

.map()

Answer 2

• Used to iterate over each element in an array, apply a transformation or operation to each element
• Return a new array containing the results of that transformation.
• It executes a provided callback function once for each element in the array and creates a new array based on the return values of the callback function.

var numbers = [1, 2, 3, 4, 5];
var multipliedNumbers = numbers.map(function(number) {
return number * 2;
});
console.log(multipliedNumbers);

Output:
[2, 4, 6, 8, 10]

Question 3

.push()

Answer 3

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

Question 4

.pop()

Answer 4

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

Question 5

.shift()

Answer 5

Removes the first element from an array and returns that element. It also shifts all subsequent elements to a lower index.

Question 6

.unshift()

Answer 6

Adds one or more elements to the beginning of an array and returns the new length of the array. It also unshifts existing elements to a higher index.

Question 7

.slice()

Answer 7

Returns a shallow copy of a portion of an array into a new array. It takes two arguments: the starting index (inclusive) and the ending index (exclusive).

Question 8

.join()

Answer 8

Joins all elements of an array into a string using a specified separator and returns the resulting string.

Question 9

.concat()

Answer 9

Combines (or concatinates) two or more arrays and returns a new array.

Question 10

.filter()

Answer 10

Creates a new array with all elements that pass a provided test.

Question 11

.split()

Answer 11

Splits a string into an array of substrings based on a specified separator.

Question 12

.trim()

Answer 12

Removes whitespace from both ends of a string.

Question 13

.includes()

Answer 13

Checks if a string contains a specified substring and returns true or false.

Question 14

.charAt()

Answer 14

Returns the character at a specified index in a string.