Juan Elfers

5.0

(2203 reviews)

US$25.00

For every 15 mins

4556

Sessions/Jobs

ABOUT ME

Sr. Full-stack Developer

JavaScript, ReactJS, and HTML/CSS expert

With more than a decade developing software (and more than 5 years at Codementor!) I always advocate for the best available solutions and the cleanest code. I also love to explain how and why things works so you can also learn more from it.

These are some of the things I can help you with: ReactJS/NextJS, Vercel, NodeJS, JavaScript/TypeScript, databases (MongoDB, SQL), Angular, Tailwind, HTML/CSS, UX/UI

Spanish, English

Buenos Aires (-03:00)

Joined July 2018

EXPERTISE

JavaScript

10 years experience | 672 endorsements

Javascript is my main language. I've been using it since I started programming and I use it every day for building websites, apps and se...

Javascript is my main language. I've been using it since I started programming and I use it every day for building websites, apps and servers. I've used several libraries and frameworks and I know the latest features of the language. If you need someone who knows Javascript, count on me!

Es6 GSAP npm JavaScript OOP CoffeeScript Handlebars.js AJAX

React

8 years experience | 295 endorsements

You've been trying to learn React but you still don't fully get it? You're not sure how hooks work, when to use them, or how the custom h...

You've been trying to learn React but you still don't fully get it? You're not sure how hooks work, when to use them, or how the custom hook you have is working? Confused about class components vs function components? useEffect, react-router, or functions like .map and .filter still don't make much sense to you? If that's the case, or if you have something in React you need to fix or implement, drop me a message, I'll have the answer

Vercel React Router Remix

Vercel React Router Remix Next.js

Node.js

7 years experience | 67 endorsements

Node is the present and future of web servers. It is not only used for serving files and database manipulation, but also for frontend eve...

Node is the present and future of web servers. It is not only used for serving files and database manipulation, but also for frontend everyday development, and that's one of the reasons why Node is so important for the web.

Express.jsNode.js express.jsPuppeteer

Express.jsNode.js express.jsPuppeteer Electron.js Socket.IO

HTML/CSS

13 years experience | 322 endorsements

I have been creating, editing, refactoring, fixing and maintaining websites for more than 10 years. I've used professionally almost any H...

I have been creating, editing, refactoring, fixing and maintaining websites for more than 10 years. I've used professionally almost any HTML feature, including the latest HTML5 tags and attributes. I use semantic, clean and organized HTML and I always choose the best possible way to create a document structure. If you need to learn HTML, CSS, or build a website, count on me; you'll see a great code quality on everything I do.

CSS3Html/css, javascript, phpSass less

CSS3Html/css, javascript, phpSass lessFull stack web developmentFull Stack

Angular

7 years experience | 24 endorsements

I've built a few Angular (+v2) and AngularJS (v1) apps and it is one of my favorite JS frameworks

Angular 2 Angular Material Design

TypeScript

7 years experience | 48 endorsements

SQL

10 years experience | 12 endorsements

REVIEWS FROM CLIENTS

5.0

(2203 reviews)

Manuel Urbina

October 2024

Helped update some CSS code for my website!

Manuel Urbina

September 2024

So knowledgable and fast! HTML skills are killer!

Bo Reahard

July 2024

He never ceases to amaze me with his knowledge and expertise.

Manuel Urbina

July 2024

Margins are always fun! He helped with that and the order of whats on the Webpage!

Israel Santana

July 2024

He is a great instructor and excels at React. After struggling for two days, I decided to reach out for help. Juan was able to teach me how to connect my PostgreSQL database to my project using Express.js. My issue was that I was fetching data into my frontend from a JSON file, and I wanted to switch to fetching from my database using Express routes. The session was supposed to be only an hour, but we ended up going for two hours, and I learned a lot. What I enjoyed the most was that he explained everything he did. He wasn't just coding; he was making sure to explain what he was doing and why he was doing it. My only regret is that I didn't record my session.

Manuel Urbina

July 2024

So good at what he does! Needed some more help with alignment, borders, padding, he got the job done!

Manuel Urbina

July 2024

Needed help with some quick code, did it effortlessly!

Kate Choi

July 2024

Juan was very professional with how he handled the code and he was able to troubleshoot the code right away.

Manuel Urbina

July 2024

Helped with webpage, aligning issues, font issues, and picture issues. He solved it quickly and I learn a little more!

Manuel Urbina

June 2024

Helped tremendously with some extra code on a hosted sight that I didn't think was something we could do. I learned something today!

SOCIAL PRESENCE

GitHub

collector-extension

JavaScript

some-coding

JavaScript

EMPLOYMENTS

Fullstack dev/mentor

Codementor

2018-10-01-Present

Full Stack Engineer @ Codementor | Top featured mentor

With over five years at Codementor, I've honed a comprehensive skill...

Full Stack Engineer @ Codementor | Top featured mentor

With over five years at Codementor, I've honed a comprehensive skill set in full-stack development, particularly in React, Node and NextJS. My mission is to deliver cutting-edge solutions that align with our organization's culture of mentorship and continuous learning. At Codementor, my role allows me to contribute diverse perspectives, building maintainable and efficient code structures that empower our clients.

My tenure at Codementor has been marked by a commitment to technology excellence, where I've leveraged ReactJS and NodeJS to develop robust applications. Tailoring solutions for a vast array of e-commerce platforms, I've helped enhance user experiences and streamline both front and backend processes. Also, my expertise in databases and APIs further complements my ability to create versatile, high-performance web services.

At Codementor I've also:

Helped and mentored hundreds of devs
Helped and teached hundreds of programming students
Worked for hundreds of clients, helping them fix, enhance and add new features to their apps and websites

My expertise in web development allows me to work on a wide range of projects and contribute immediately. Working with so many people and projects has enabled me to quickly understand any codebase and make effective changes.

HTML/CSS

PHP

Python

HTML/CSS

PHP

Python

Node.js

Angular

TypeScript

Firebase

React

JavaScript

React Router

Redux

Next.js

Tailwind css

React Hooks

React Testing Library

Vercel

React Query

Next UI

AWS

Sr. Frontend Engineer

AutoComplete

2021-12-01-2022-07-01

Worked as a UI/Product Engineer in client-side applications and mobile devices. Joined a fresh team at the start-up, building most of ...

Worked as a UI/Product Engineer in client-side applications and mobile devices. Joined a fresh team at the start-up, building most of the mobile web from scratch.
Developed in a rapidly changing environment, making changes and adjustments on a fast-paced demand.

Introduced TypeScript and TDD for improved maintainability in the project, while adapting to a growing team which required working on our communication skills and tasks assignment.

TypeScript

React

Test Automation

TypeScript

React

Test Automation

Tailwind css

Frontend Developer

Fizzmod

2016-02-01-2018-09-01

At Fizzmod I developed high-traffic e-commerce websites over the Vtex platform. Worked with Product to develop unique experiences inte...

At Fizzmod I developed high-traffic e-commerce websites over the Vtex platform. Worked with Product to develop unique experiences integrating disparate sources of data into a seamless experience. Additionally built multiple desktop applications with ElectronJS for optimized applications.

HTML/CSS

Angular

React

HTML/CSS

Angular

React

JavaScript

Electron

PROJECTS

PokeArgentum e-commerceView Project

2024

I wanted to showcase this project not only because it's one of the latest I've been working on, but also because: - I built it from scra...

I wanted to showcase this project not only because it's one of the latest I've been working on, but also because: - I built it from scratch using the latest libraries and features available, such as Next.js 14, NextUI, and the newest Vercel storage features. - We developed a fully functional MVP in just 45 days, demonstrating that I can deliver quickly when we prioritize what truly matters. - I made 100% of the decisions on this project, from design to functionality, including marketing and product decisions.

Next.js

Next UI

Next.js

Next UI