How do I test this regex in JavaScript and TypeScript?

Use regex.test(): const regex = /([a-z0-9])([A-Z])/g; const isValid = regex.test(inputString);

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

A valid matching string is "devTransformHub". A non-matching string is "lowercase".

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 LibraryCamelCase Word Boundary Regex

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CamelCase Word Boundary Regex

Identifies transitional word boundaries in camelCase and PascalCase identifiers to convert strings into snake_case or kebab-case.

Regular Expression Pattern:

/([a-z0-9])([A-Z])/g

Valid Match Example:

devTransformHub

Invalid / Non-Match Example:

lowercase

Regex Syntax Breakdown & Explanation

•([a-z0-9]) : Captures preceding lowercase letter or digit
•([A-Z]) : Captures subsequent uppercase letter initiating new word

Implementation in Popular Languages

JavaScript / TypeScript

const regex = /([a-z0-9])([A-Z])/g;
const isValid = regex.test("devTransformHub");
console.log(isValid); // true

Python (re)

import re

pattern = r"([a-z0-9])([A-Z])"
match = re.match(pattern, "devTransformHub")
print(bool(match)) # True

Go (regexp)

package main
import (
  "fmt"
  "regexp"
)

func main() {
  re := regexp.MustCompile(`([a-z0-9])([A-Z])`)
  fmt.Println(re.MatchString("devTransformHub"))
}

Frequently Asked Questions

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

The regular expression pattern is /([a-z0-9])([A-Z])/g. Identifies transitional word boundaries in camelCase and PascalCase identifiers to convert strings into snake_case or kebab-case.