Question

I’m trying to write a regular expression that will accept the following:

s#.#
f#.#

Where # can be an integer of any size (so really, a decimal preceded by s or f). I also need this to accept nothing else. So if it’s something like:

As#.# would not be accepted because there's an A before the s
s#.#X would not be accepted because there's an X after the decimal.

There will always be either an s or an f to start, then a number, a period, and another number. All those parts are required and the numbers can be any size and any number of integers.

Answer 1

Try this regular expression:

/^[sf]\d+\.\d+$/

Explanation

• ^ is an anchor that matches the start of the string.
• [sf] is a character class and means an s or an f.
• \d means a digit.
• + means one or more.
• \. matches a literal dot.
• $ is an anchor that matches the end of the string.