JavaScript Video Tutorial - Using countBy() function in UnderscoreJS

In this demonstration, we will use countBy() function to count the number of items per group in a collection of objects.

[manishjoshi]

Hello Toptal team
If you give demo code which you demonstrating here then that would be very help full for us because in your example they are inter related to _map, and other methods .so when i am trying to do practice it given some problem
thank in advance :)