Whenever we say that something executes or happens client-side, or on the client, it's important to understand that what we mean by client is the user's web browser.
While it's important to understand the underlying architecture on which ServiceNow runs for server-side scripting, client-side scripting grants you access to a whole new set of non-ServiceNow APIs: The DOM (Document Object Model), and ServiceNow APIs which together, grant you the ability to directly modify what the user sees and how they interact with the presentation layer of the system, without modifying any back-end logic or data. You can change field labels, choice list options, flash or highlight a field, throw an alert or confirm dialog, request input from the user, and more.
In this chapter, we'll learn about:
Security
Compatibility
Building for performance
UI Scripts
Best practices