KEYBOARD SHORTCUTS FOR PAGINATION
The custom callback function code detects which one of the two keyboard arrow keys were pressed: left or right. It then selects a corresponding pagination link and simply simulates (triggers) a click event for it.
Computers have multiple input devices for easier usage. Imagine entering text without a keyboard or using a website without a mouse. Therefore we, people who make websites, should enable these devices on our products. The most basic but very useful thing would be keyboard shortcuts for pagination.