Building a Telephone Number Validator Project in React

Have you ever filled out a form and wondered if your number was accepted only because of the format? As someone diving deep into front-end development, I noticed how often this detail is overlooked. That’s when I decided to take on a practical challenge that every web form needs, a Telephone Number Validator Project.

Let’s be honest, regex isn’t the most glamorous tool in our coding toolkit, but it’s wildly powerful. Pair it with React, throw in some real-time feedback magic, and you’ve got yourself an engaging, educational, and highly functional tool that will level up any portfolio.

🛠️ Why I Chose to Build a Telephone Number Validator

As I continued building my portfolio (after projects like the Roman Numeral Converter: Bridging History and Code), I realized many coding challenges lack immediate real-world usability. So, I wanted something that would not only challenge me logically but also have tangible, functional results.

Validating phone numbers is deceptively complex, formats vary wildly by country, optional parentheses, dashes, international codes…you get the picture. The Telephone Number Validator Project felt like the perfect next step.

This also aligns with my goals for the rest of the year, as I outlined in my post. “Next Steps in My Coding Journey: What I’m Focusing on for the Rest of 2024”.

🔍 Planning the Validator: What Features I Prioritized

Creating a plan was the first and most essential step. I outlined these key features:

• Basic format validation (xxx-xxx-xxxx, (xxx) xxx-xxxx)
• International number support (+xx xxx xxx xxxx)
• Real-time feedback on form input
• User-friendly error messages
• Clean and responsive design in React

Each of these came with its own set of mini-challenges, and spoiler alert—they were very satisfying to overcome!

📐 Developing the Regex Logic in JavaScript

Regex: the developer’s best frenemy.

Let’s break down the validation logic that powered this project. Here’s a simplified version:

const validatePhoneNumber = (input) => {
  const regex = /^\+?([0-9]{1,3})?[-.\s]?\(?([0-9]{3})\)?[-.\s]?([0-9]{3})[-.\s]?([0-9]{4})$/;
  return regex.test(input);
};

This pattern checks for international codes, optional symbols, and variations in formatting.

For more regex examples, I leaned on Regular Expressions 101 and MDN Web Docs to build and test patterns.

Pro tip: Always test regex with a wide variety of cases. Unexpected inputs are more common than you think.

⚛️ Building the Interface in React: Real-Time Feedback

React makes interactive feedback so smooth. My input field component watches the user’s keystrokes and validates each change. Here’s a simplified snippet:

<input 
  type="text" 
  value={phoneNumber} 
  onChange={(e) => {
    setPhoneNumber(e.target.value);
    setIsValid(validatePhoneNumber(e.target.value));
  }}
  className={isValid ? 'valid' : 'invalid'}
/>

This gave instant feedback and used conditional styling to indicate whether the input was correct. If the number was invalid, a helpful message appeared below the input field.

Adding this visual response elevated the user experience significantly. No more guessing if the form will throw an error after submission.

🤯 Challenges I Faced (and How I Solved Them)

Creating a Telephone Number Validator Project that accounts for multiple formats isn’t easy. Here are some curveballs I ran into:

• Handling spaces and symbols: Some users input with dashes, others with dots, some even with nothing. I had to make sure my regex could interpret all of it.
• Country code confusion: Sometimes users add a country code but with the wrong format.
• Edge cases: Numbers that are technically valid but not realistically used (like 000-000-0000).

Through trial, error, and lots of console logs, I refined my function to be inclusive but precise.

📚 FAQ: All About the Telephone Number Validator Project

Q: Can this validator handle numbers outside the U.S.?
A: Yes! I included support for international numbers by allowing for optional country codes like +44, +27, etc.

Q: How did you test the validator?
A: Manually entered a range of phone numbers and used unit testing to ensure consistency.

Q: Will you add more features in the future?
A: Definitely! I’m considering adding automatic formatting and deeper validation tied to specific countries.

Q: Where can I see the live project?
A: I’ll be adding this to my portfolio soon—stay tuned!

💬 A Story from Development: The Regex Breakdown

During one late-night coding session, I realized my validator kept rejecting phone numbers from South Africa. Even though the format was technically correct. I stared at the regex for what felt like hours, tweaking parentheses and backslashes.

Then I discovered I’d forgotten to account for a space between the international code and the local number. One tiny oversight. One huge lesson in regex precision. That’s when I knew I had to build flexibility into the pattern.

It reminded me of my learning journey in “CS50 Week 2: My First Steps in Data Handling with Arrays and Cryptography” The smallest logic misstep can cause a ripple effect.

✅ What I Learned: Solving Practical Problems Elegantly

This project taught me that coding isn’t just about logic, it’s about empathy. Thinking from the user’s perspective shaped how I handled feedback, validation errors, and even styling.

More importantly, it showed me the magic of solving real-world problems with elegant, accessible tools. And it helped me solidify my understanding of:

• JavaScript regex fundamentals
• State management and conditional rendering in React
• UX design principles around input forms

❓What Do You Think?

Have you ever built your own validation tool or worked with regex? What challenges did you face, or are you nervous to try it? I’d love to hear about your experiences and help troubleshoot if you’re planning to build your own Telephone Number Validator Project!

👋 Let’s Connect!

Thanks for reading about my Telephone Number Validator Project! I’m building in public and would love for you to join the journey. If you’re working on your own coding journey or just starting out, I’d love to hear about your experiences and challenges. Drop a comment below or reach out to me through my contact page to connect!

🚀 What projects are you working on? Share in the comments or follow me on TikTok and Instagram @CodeWithMalie.

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And if you enjoyed this post, you might also like: “The Most Useful JavaScript Concepts I’ve Learned So Far”.