The validation succeeds only if the user input matches the pattern.
Regular expressions let you check input text for a wide variety of custom conditions for which the input must follow a specific pattern.
This API consists of a set of methods and properties available on each form element.
For example, use two backslash characters (\) to represent a backslash character.
The following rules govern regular expressions that match a single character: th parenthesized subexpression.
Form validation helps us achieve these goals — this article tells you what you need to know.
This is called form validation — when you enter data the web application checks it to see if it is correct.