Why is a js script running faster outside of a tab in a browser js?

Question

Socket.io

Hello, I have a task to make a script with large calculations and for this I decided to interact with socket.io . The bottom line is that the client part only gives, let's say, the ID that the server needs to perform, and the server already performs a series of calculations and returns the result.
Now, to the point, when I am in the browser on this tab, the same calculation is performed in 24 seconds and when I am in another browser tab, the calculation is performed in 3 seconds, why is this happening?

Answer 1

caching