Regular Expression Match to test for a valid year

Question

Given a value I want to validate it to check if it is a valid year. My criteria is simple where the value should be an integer with 4 characters. I know this is

Answer 1

You need to add a start anchor ^ as:

^\d{4}$

Your regex \d{4}$ will match strings that end with 4 digits. So input like -1234 will be accepted.

By adding the start anchor you match only those strings that begin and end with 4 digits, which effectively means they must contain only 4 digits.