Validation of phone number in Onepage forms (onepage.io) without SMS confirmation

Good day.

I have worked on similar tasks in Webflow, Tilda, and other builders where there is no access to the backend and everything is resolved through client-side logic. In your case, I would implement a solution using libphonenumber in conjunction with my own submit interception logic, rather than using a simple regex. For the German market, this will provide a much more accurate validation, especially with varying lengths of numbers.
I can implement normalization to E.164 before form submission and block the submit with a correct message in German. The field will be highlighted, and the error will disappear after correction. If needed, we can add a light mask or intl-tel-input without conflicts with Onepage scripts.
We will ensure stability by searching for elements by field type and form context, rather than by dynamic IDs. If necessary, we will use MutationObserver to ensure the script correctly "catches" the form even during asynchronous rendering.
Please let me know if there is one form on the page or several, and if there is a possibility to insert the code globally for the entire site? This will affect the binding method.

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Hello! I am interested in your project for phone validation in forms on Onepage.

I have experience integrating custom JavaScript into website builders (intercepting submit, working with dynamic DOM, MutationObserver, cross-browser compatibility).

I propose a solution: Validation through libphonenumber (for Germany), blocking submission for incorrect numbers, notifications in German and highlighting the field, normalizing the number to E.164 format (+49…), filtering 0000000000;

The solution will work without SMS, reliably on desktop and mobile, without conflicts with other scripts.

I am ready to implement it quickly and provide instructions for integration.

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Ready to perform.
Experience in Web Development over 12+.
Examples of work https://koder.pp.ua/portfolio/

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Good day!
My name is Dmytro, from King Kong Web.

I have reviewed your technical specifications for Onepage. We can implement client-side validation of the phone number without SMS, so that the form is not submitted with "junk" numbers, and the user immediately sees an error.

We will achieve this by inserting custom JavaScript into Onepage: we will hook into the form's submit event, check the number at two levels (basic validation + rules for DE/+49), and in case of an error, we will block the submission and show a message in German. We will also add highlighting to the field, and when the number is corrected, the error will disappear.

Regarding the approach: it is optimal to use libphonenumber (via CDN) to correctly validate German numbers and, if necessary, normalize them to E.164 format before submission. If Onepage does not allow for stable integration of the library, we will implement a reliable fallback based on length/pattern rules (regex + logic against 0000/too short).

… After completion, we will provide the ready code for insertion, a brief instruction on where exactly to add it in Onepage, which selectors we are using, and how to check the functionality on desktop/mobile.

We are ready to start immediately. If needed, please send a link to the page with the form or a screenshot/HTML structure to quickly determine the most stable way to connect.

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Good day, Valery.

I choose libphonenumber instead of regex. This will ensure accurate verification of German numbers (+49), normalization to E.164, and blocking of fakes. I will integrate it through Custom Code, using MutationObserver for stability with the dynamic DOM.

Users will see clear error messages in German, and submission will be blocked until the data is corrected. You will receive the finished code and instructions that guarantee the cleanliness of the database without degrading conversion.

I am ready to provide the complete code and instructions for integration into Onepage.

Additionally, instead of basic validation, I suggest expanding the functionality to an intelligent input mask for the phone number (based on intl-tel-input). This will significantly improve UX by automatically formatting the number during input and highlighting the correct format for Germany. It is also possible to add automatic country detection by prefix, which will simplify input for users from other countries in the future.

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Hi,

I can implement phone number validation for your Onepage forms. I have experience with JavaScript client side validation, working with form builders, and DOM manipulation for dynamic environments.

I will create a validation script that blocks submission of invalid German phone numbers like 0000000000, short numbers, and repeated patterns, validates both +49 and local 0 formats using Google libphonenumber library for accurate German number validation, shows error messages in German with red border highlighting, normalizes valid numbers to E.164 format before submission, and works reliably on desktop and mobile browsers.

Regarding Onepage.io experience, I haven't worked directly with Onepage.io but I have experience integrating custom JavaScript into platforms like Webflow and Wix where similar challenges exist with dynamic IDs and async form loading. The approach is similar using stable selectors, MutationObserver for async loading, and event delegation.

For the approach I recommend using libphonenumber via CDN lightweight version like google libphonenumber js. This is more reliable than regex for German numbers which have variable length. Regex can work as fallback but won't catch all edge cases.
…
For E.164 normalization, libphonenumber can normalize valid numbers to E.164 format before form submission which helps with CRM data consistency.

For DOM stability I'll use multiple fallback selectors like input type tel, placeholder text, and label text, and implement MutationObserver to reattach validation if the form reloads asynchronously. I'll also test for multiple forms on the page and target the correct one.

I will deliver ready to use JavaScript code with CDN library links, integration instructions, selector documentation, and optional CSS for error styling.

Timeline: 1 week
Cost: $400 to $500 USD

I am available to start working immediately.

Youssef

Hello, write to me in private messages.

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Hello. I have been working with JavaScript for over 8+ years. I am ready to set up input validation. Feel free to contact me.

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Hello! I have carefully studied your project and am ready to start its implementation. Let's discuss the details for the best execution.

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Good day. I have done similar tasks, but not on onepage. The function to insert your own code is available in paid versions - so I cannot check something. I cannot say whether it will work or not. But I do have experience overall, and I personally need to figure it out "on the spot." If it suits you, please reach out. I have done: Script for unifying mobile numbers - it is in my portfolio.

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Hello, Valerii Shcherbakov.
I've checked your requirements more carefully.
I can fully build the section using library(libphonenumber or other) and a few custom functions.
In this case, I don't need to change DOM for this.
I will add new section(for error) only.
I hope to make contract with you.
Thank you.

Good evening. Your task is completely clear to me. I know how to solve your problem, I will write all the necessary functionality with the required validation. The numbers will be correct, everything as you want...

I will do additional checks, you will be very satisfied with the result!!!

I am waiting for you in personal messages.

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Ready to execute right now, I will deliver the code in an hour. Experience of more than 4 years.

Responses:
1) Yes. The approach I use is universal for any no-code builders.
2) Definitely libphonenumber-js as the main approach.
3) Yes, it is possible.
4) Cascade selectors: the script searches for the field not by a single ID or class, but by a chain of 7 selectors (type tel, attributes name, placeholder). Even if Onepage changes one — another will work.

P.S. Write to me in private messages, I already have a ready solution.

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Good evening, I will complete the task in 1 hour, if you are interested, write to me, I will be happy to collaborate.

upd: I already have the ready code, just need to integrate it into your form, a link is needed.

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Hello.

I am ready to take it on. Write to me, we will discuss.

1. I have experience with constructors.
2. We can try using regex.
3. Yes.
4. This question requires a more detailed answer.

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