Only enter numbers: "^[0-9]*$"
Only n-digit numbers can be entered: "^d{n}$"
Only at least n digits can be entered: "^d{n,}$"
Only the number of m-n bits is entered: "^d{m,n}$"
Only numbers starting with zero and non-zero are entered: "^(0|1-9*)$"
Only positive real numbers with two decimal places can be entered: "^[0-9]+(.[0-9]{2})?$"
Only positive real numbers with 1-3 decimal places can be entered: "^[0-9]+(.[0-9]{1,3})?$"
Only non-zero positive integers can be entered: "^+?1-9*$"
Only non-zero negative integers can be entered: "^-1-9*$"
Only characters with length 3 can be entered: "^.{3}$"
Only strings composed of 26 English letters can be entered: "^[A-Za-z]+$"
Only strings composed of 26 capital English letters can be entered: "^[A-Z]+$"
Only strings composed of 26 lowercase English letters can be entered: "^[a-z]+$"
Only strings composed of numbers and 26 English letters can be entered: "^[A-Za-z0-9]+$"
Only strings composed of numbers, 26 English letters or underscores can be entered: "^w+$"
Verify user password: "^[a-zA-Z]w{5,17}$" is the correct format: start with a letter, length between 6-18