Common array operations in Javascript - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the push() method do in an array?

It adds one or more elements to the end of an array and returns the new length of the array.

beginner

How do you remove the first element from an array?

Use the shift() method. It removes the first element and returns it, shifting all other elements down by one index.

intermediate

What is the difference between map() and forEach()?

map() creates a new array by applying a function to each element, while forEach() simply runs a function on each element without returning a new array.

beginner

How can you find the index of a specific element in an array?

Use the indexOf() method. It returns the first index at which the element can be found, or -1 if it is not present.

intermediate

What does the filter() method do?

It creates a new array with all elements that pass a test implemented by a provided function.

Which method adds elements to the end of an array?

A pop()

B unshift()

C shift()

D push()

The push() method adds elements to the end of an array.

What does the pop() method do?

A Removes the first element

B Removes the last element

C Adds an element at the start

D Adds an element at the end

pop() removes the last element from an array and returns it.

Which method creates a new array by applying a function to each element?

A map()

B reduce()

C filter()

D forEach()

map() applies a function to each element and returns a new array.

How do you find the position of an element in an array?

A filter()

B find()

C indexOf()

D slice()

indexOf() returns the index of the first occurrence of an element.

Which method returns a new array with elements that pass a test?

A filter()

B map()

C reduce()

D forEach()

filter() returns a new array with elements that pass the test function.

Explain how to add and remove elements from the start and end of an array in JavaScript.

Think about methods that work at the beginning and end of the array.

Describe the difference between map(), forEach(), and filter() methods.

Focus on what each method returns and how they process array elements.