Juan Elfers

5.0

(2176 reviews)

US$25.00

For every 15 mins

4516

Sessions/Jobs

Featured mentor of the week

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 / Remix / Supabase
NodeJS / Express
JavaScript / Typescript
Databases (SQL, Postgres, Mongo, Firestore, ...)
Puppeteer (NodeJS)
HTML + CSS/Sass/Tailwind
Angular
Git
npm
UX / UI
PHP

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

7 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

5 years experience | 64 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 | 200 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.

HTML5 CSS3Html/css, javascript, php

HTML5 CSS3Html/css, javascript, phpHTMLSass lessFull stack web developmentFull Stack

CSS3

13 years experience | 236 endorsements

I know in depth all the CSS potential with it's media queries, flex and grid layout, animations, transitions and every thing that can be ...

I know in depth all the CSS potential with it's media queries, flex and grid layout, animations, transitions and every thing that can be styled and manipulated with this great language. I also use Sass/SCSS pre-processors everyday to be more time efficient and to improve code quality. Just let me know if you need some help with CSS.

Sass LESS

jQuery

10 years experience | 179 endorsements

jQuery has been here for a while and had always helped us to write shorter and cleaner code, more maintanable and easier to read. If you ...

jQuery has been here for a while and had always helped us to write shorter and cleaner code, more maintanable and easier to read. If you want someone who knows and really understands this great classic library then I am here to help.

jQueryHtml5, css3 and jqueryjQuery Mobile

jQueryHtml5, css3 and jqueryjQuery Mobile jQuery UI

Solidjs

1 year experience | 8 endorsements

The syntax is very similar to ReacJS; it actually uses JSX. But the performance of SolidJS is outstanding and this is one of the reasons ...

The syntax is very similar to ReacJS; it actually uses JSX. But the performance of SolidJS is outstanding and this is one of the reasons you should be using it. Ping me if you need some help with Solid!

React JavaScript

REVIEWS FROM CLIENTS

5.0

(2176 reviews)

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!

Manuel Urbina

June 2024

Best guy to help troubleshoot!

Manuel Urbina

June 2024

Needed a form added and beautified!

SOCIAL PRESENCE

GitHub

collector-extension

JavaScript

some-coding

JavaScript

EMPLOYMENTS

Fullstack dev/mentor

Codementor

2018-10-01-Present

Freelancer and tutor @ Codementor
• Participated in an extensive range of jobs from frontend to backend.
• Tutored and helped ...

Freelancer and tutor @ Codementor
• Participated in an extensive range of jobs from frontend to backend.
• Tutored and helped plenty of programmers, mainly in Javascript, React, Node, jQuery and HTML/CSS
• Worked with and helped hundreds of programmers and programming students during the last 4 years
• Gained experience working on a very diversified kind of projects

HTML/CSS

PHP

Python

HTML/CSS

PHP

Python

Node.js

Angular

Firebase

React

JavaScript

Redux

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

Fullstack Developer

Freelancer

2010-01-01-2016-01-01

During my first years as a developer, I worked with PHP and MySQL building CRUD systems for small businesses. I also developed several...

During my first years as a developer, I worked with PHP and MySQL building CRUD systems for small businesses. I also developed several websites from scratch, including the designs, and worked on different requirements from these same businesses, such as email marketing and hosting configuration.

HTML/CSS

PHP

jQuery

HTML/CSS

PHP

jQuery

MySQL

CodeIgniter

JavaScript

PROJECTS

Puppeteer automatisms

2021

JavaScript

Puppeteer

JavaScript

Puppeteer