How do I test this regex in JavaScript and TypeScript?

Use regex.test(): const regex = /^\d{5}(?:-\d{4})?$/; const isValid = regex.test(inputString);

What is an example of a matching and non-matching string?

A valid matching string is "94016-1234". A non-matching string is "9401".

Is this regex safe from ReDoS (Catastrophic Backtracking)?

Yes, this pattern is optimized for linear execution time and safe for browser-side validation without locking up the UI thread.

HomeRegex LibraryUnited States Postal ZIP Code Regex

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United States Postal ZIP Code Regex

Matches 5-digit US ZIP codes and standard 9-digit ZIP+4 formats (12345 or 12345-6789).

Regular Expression Pattern:

/^\d{5}(?:-\d{4})?$/

Valid Match Example:

94016-1234

Invalid / Non-Match Example:

9401

Regex Syntax Breakdown & Explanation

•^\d{5} : Mandatory 5-digit base postal zone
•(?:-\d{4})?$ : Optional hyphen and 4-digit routing extension

Implementation in Popular Languages

JavaScript / TypeScript

const regex = /^\d{5}(?:-\d{4})?$/;
const isValid = regex.test("94016-1234");
console.log(isValid); // true

Python (re)

import re

pattern = r"^\d{5}(?:-\d{4})?$"
match = re.match(pattern, "94016-1234")
print(bool(match)) # True

Go (regexp)

package main
import (
  "fmt"
  "regexp"
)

func main() {
  re := regexp.MustCompile(`^\d{5}(?:-\d{4})?$`)
  fmt.Println(re.MatchString("94016-1234"))
}

Frequently Asked Questions

Everything you need to know regarding specifications, syntax, and security best practices.

The regular expression pattern is /^\d{5}(?:-\d{4})?$/. Matches 5-digit US ZIP codes and standard 9-digit ZIP+4 formats (12345 or 12345-6789).