How to Regex a string

Question

Is it possible to check with regex:

1. the complete string are numbers AND
2. the first character is a 7 or 8 then the complete length of the st

Answer 1

Here's the regex: /^[78]\d{10}$/

"^" indicates the start of the line "$" indicates the end of the line \d means digits {10}means exactly 10 [] is a group of valid values

The second question is dependant on wether your Engine supports Lookahead and Lookbehind https://www.regular-expressions.info/conditional.html