vbscript is used for server side as well as client side where as java script is used for client side only.

Webpages, either the files by themselves, or through a server-side script.

A script on Roblox runs on the server side then talks to the users. This allows it to address multiple users and manage the server. Local scripts run on a users computer then talks to the server. This allows for less lag in tools.

It is not impossible to code on server side using javascript as there are frameworks available today which lets use of javascript on server side. But usage of this is not that high as most people prefer the normal way of using AJAX if they want javascript to interact with a server side language.

Java Script alone has no value. It has to be used in association with various server side technologies and other languages. There are certifications available on java script but it would be more prudent to get certified in industry recognized certifications primarily on server side technologies.