Some resources also refer to Jscript (Microsoft) and ECMAScript (European Computer Manufacturer's Association), but these are both derivatives of Java Script.
Since only Microsoft Internet Explorer supports VBScript, you'll probably choose Java Script as your primary scripting language to use on a user's computer.
There are already some examples available; have a look at Regular Expressions for Webform Validation (thx nfd) and for more examples.
Most often, the purpose of data validation is to ensure correct user input.
Validation can be defined by many different methods, and deployed in many different ways.
Hopefully these behaviours will converge in future releases.
For these examples we have created our own valid/invalid CSS formatting to override the browser default. That's why you may see something like the following: Before you type anything into the box a red marker is shown.