map specifically

Question 1

What does the map() method do in JavaScript?

Answer 1

It creates a new array by calling a provided function on every element in the original array.

Question 2

Does map() modify the original array?

Answer 2

No, map() does not modify the original array. It returns a new array with transformed values.

Question 3

What arguments does the callback function in map() take?

Answer 3

The callback function takes up to three arguments: currentValue, index, and the original array.

Question 4

What is the syntax of map()?

Answer 4

array.map(function(currentValue, index, array) { /* code */ }, thisArg);

Question 5

Give a simple example of using map().

Answer 5

const nums = [1, 2, 3]; const doubled = nums.map(n => n * 2); // [2, 4, 6]

Question 6

How is map() different from forEach()?

Answer 6

map() returns a new array with transformed data, while forEach() just executes a function for each element and returns undefined.

Question 7

Can you chain map() with other array methods?

Answer 7

Yes, map() is often chained with filter(), reduce(), or other methods for data transformation.

Question 8

What happens if the callback in map() does not return anything?

Answer 8

If the callback doesn’t return a value, map() will fill the new array with undefined values.

Question 9

Can map() be used on non-array objects?

Answer 9

Only on array-like objects that implement map(), like typed arrays or when converted using Array.from().

Question 10

Is map() synchronous or asynchronous?

Answer 10

map() is synchronous — it doesn’t wait for async operations inside the callback to finish.