adresses mail ^[a-z0-9.-]+@[a-z0-9.-]{2,}\.[a-z]{2,4}$

1 lettre, 1 chiffre, 1 caractère spécial au moins Chaine comprise entre 8 et 15 caractères ^(?=.[A-Za-z])(?=.\d)(?=.[&-+!$@%])([&-+!*$@%\w]{8,15})$

Recovers the part before @ For example: teste@testregex.com The regex will catch teste

Removes the last 4 digits from a expression

MASK TO VALIDATION, WHEN YOU NEED THE AREA CODE OPEN. TO A CELLPHONE WITH 9 OR 8 DIGITS + AREA CODE OF 2 DIGITS 11 987654321 -> IT WILL GET 98765

Matches x only if x is not preceded by y.This is called a negated lookbehind. For example, /(?<!-)\d+/ matches a number only if it is not preceded by a minus sign. /(?<!-)\d+/.exec('3') matches "3". /(?<!-)\d+/.exec('-3') match is not found because the number is preceded by the minus sign.