Regular Expressions in JavaScript

Here is a full JavaScript program that demonstrates how to use regular expressions for pattern matching and string manipulation:

This program creates a simple web page with an input field for an email address, a button labeled "Validate" and an empty p element to display the validation results.

The program uses a regular expression to match the pattern of a valid email address. The regular expression is created using the /.../ syntax and it uses a combination of special characters and characters classes to match the pattern. The regular expression is stored in the emailRegex variable.

When the "Validate" button is clicked, the program uses the test() method of the regular expression to check if the email address entered in the input field matches the email pattern. If the email address is valid the program changes the innerHTML of the output element to "Valid email" otherwise it changes it to "Invalid email".

This script can be implemented in any software that supports HTML and JavaScript, such as a text editor like Sublime or Atom, and a web browser like Chrome, Firefox or Safari.