refactor: update email validation regex to RFC 5322 compliant version (#2126)

Author: afislonge

Specialized Areas/Regular Expressions/Email Address Validation/README.md

@@ -1,11 +1,48 @@
-## Email Address Validation
+# Email Address Validation
 
-This regular expression checks if the provided string matches the common pattern for email addresses.
+This project provides email validation functionality in pure JavaScript. It includes a refactored regex implementation that covers common RFC 5322 patterns and stricter domain rules.
 
-**Please note that the code is based on ES2021, and as such, will not work in the global scope or scopes that are not ES2021 compatible.**
+---
 
-^[a-zA-Z0-9._%+-]+: Matches one or more characters that can be letters (both uppercase and lowercase), digits, dots, underscores, percent signs, or plus or hyphen signs at the start of the string.
-@: Matches the "@" symbol.
-[a-zA-Z0-9.-]+: Matches one or more characters that can be letters, digits, dots, or hyphens in the domain part of the email address.
-\.: Matches a dot.
-[a-zA-Z]{2,}$: Matches two or more letters at the end of the string, representing the top-level domain (TLD) of the email address.
+## Refactored Email Validation (2025 Update)
+
+The regex has been improved to handle edge cases in the local part, domain, and top-level domain (TLD).
+
+### Key Features
+
+- Supports letters, digits, and allowed special characters in the local part:  
+  `!#$%&'*+/=?^_`{|}~-`
+- Supports dots in the local part, but not consecutive dots.
+- Supports quoted local parts, e.g., `"john.doe"@example.com`.
+- Validates domain labels:
+  - Letters, digits, and hyphens (`-`)
+  - Labels cannot start or end with a hyphen
+  - No consecutive dots
+- Restricts TLD length to 2–63 characters.
+- Supports IPv4/IPv6 literals in brackets, e.g., `user@[192.168.0.1]`.
+
+### Example Usage
+
+```js
+const emailRegex = /^(?:[a-zA-Z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-zA-Z0-9!#$%&'*+/=?^_`{|}~-]+)*|"(?:(?:\\[\x00-\x7f]|[^\\"\r\n])*)")@(?:(?:[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?\.)+[a-zA-Z]{2,63}|\[(?:(?:25[0-5]|2[0-4][0-9]|1?[0-9]{1,2})\.){3}(?:25[0-5]|2[0-4][0-9]|1?[0-9]{1,2}|[a-zA-Z0-9-]*[a-zA-Z0-9]:[^\]]+)\])$/;
+
+function validateEmail(email) {
+  return emailRegex.test(email);
+}
+
+const emails = [
+  "example@email.com",
+  "user.name+tag@example.co.uk",
+  '"quoted.user"@example.com',
+  "user@[192.168.1.1]",
+  "user@-example.com",
+  "user@example..com",
+  "user@example-.com",
+  "user@.example.com"
+];
+
+emails.forEach(email => {
+  console.log(email, validateEmail(email) 
+    ? "is valid" 
+    : "is invalid");
+});

Specialized Areas/Regular Expressions/Email Address Validation/isEmail.js

@@ -1,9 +1,22 @@
-const emailRegex = /^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/;
+//const emailRegex = /^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/;
 
-const email = "example@email.com";
+//refactor emailRegex
+const emailRegex = /^(?:[a-zA-Z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-zA-Z0-9!#$%&'*+/=?^_`{|}~-]+)*|"(?:(?:\\[\x00-\x7f]|[^\\"\r\n])*)")@(?:(?:[a-zA-Z0-9](?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?\.)+[a-zA-Z]{2,63}|\[(?:(?:25[0-5]|2[0-4][0-9]|1?[0-9]{1,2})\.){3}(?:25[0-5]|2[0-4][0-9]|1?[0-9]{1,2}|[a-zA-Z0-9-]*[a-zA-Z0-9]:[^\]]+)\])$/;
 
-if (emailRegex.test(email)) {
-  console.log("Valid email address");
-} else {
-  console.log("Invalid email address");
-}
+const emails = [
+  // Valid emails
+  "example@email.com",
+  "user.name+tag@example.co.uk",
+  '"quoted.user"@example.com',
+  "user@[192.168.1.1]",
+
+  // Invalid emails (should fail)
+  "user@-example.com",
+  "user@example..com",
+  "user@example-.com",
+  "user@.example.com"
+];
+
+emails.forEach(email => {
+  console.log(email, emailRegex.test(email) ? "is valid email addres" : "is invalid email address");
+});