Modern JavaScript from the Beginning - Second Edition - Array.map Method

The video tutorial explains the use of high-order array methods like filter and map in JavaScript. It demonstrates how map can be used to transform arrays by applying a function to each element, with examples including doubling numbers and extracting company data. The tutorial also covers using forEach as an alternative to map, chaining map methods for complex operations, and combining different methods like filter and map for advanced data manipulation.

What is the primary difference between the 'filter' and 'map' methods in JavaScript?

• Filter can only be used with numbers, while map can be used with any data type.

• Filter returns a new array based on a condition, while map transforms each element.

• Filter and map are identical in functionality.

• Filter modifies the original array, while map does not.

In the example of doubling numbers using 'map', what is the result of mapping the array [1, 2, 3, 4, 5]?

• [3, 6, 9, 12, 15]

• [2, 4, 6, 8, 10]

• [1, 2, 3, 4, 5]

• [0.5, 1, 1.5, 2, 2.5]

How does the 'forEach' method differ from 'map' when doubling numbers in an array?

• forEach returns a new array, while map does not.

• forEach can only be used with strings, while map can be used with numbers.

• forEach does not return a new array, while map does.

• forEach modifies the original array, while map does not.

When using 'map' with an array of company objects, how can you extract only the company names?

• By using a 'forEach' loop.

• By mapping each company object to its 'name' property.

• By using a 'reduce' method.

• By using a 'filter' method.

What is the result of mapping an array of company objects to include only their names and categories?

• An array of numbers representing company IDs.

• An array of booleans indicating company status.

• An array of objects with name and category properties.

• An array of strings with company names.

How can you calculate the length of each company in years using 'map'?

• By dividing the start date by the end date for each company.

• By multiplying the start date by the end date for each company.

• By adding the start date to the end date for each company.

• By subtracting the start date from the end date for each company.

What is the purpose of chaining multiple 'map' methods?

• To modify the original array.

• To perform sequential transformations on array elements.

• To filter out unwanted elements.

• To sort the array in ascending order.

How can you chain 'filter' and 'map' methods to first filter even numbers and then double them?

• By using 'filter' to select even numbers and 'map' to double them.

• By using 'reduce' to select even numbers and 'map' to double them.

• By using 'forEach' to select even numbers and 'map' to double them.

• By using 'map' to select even numbers and 'filter' to double them.

What is the result of filtering the array [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] to get even numbers and then doubling them?

• [1, 3, 5, 7, 9]

• [4, 8, 12, 16, 20]

• [2, 4, 6, 8, 10]

• [3, 6, 9, 12, 15]

What is a key benefit of chaining different array methods like 'filter' and 'map'?

• It allows for modifying the original array.

• It reduces the array to a single value.

• It enables complex data transformations in a concise manner.

• It automatically sorts the array.