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Hire our Elite JavaScript Developers

FullStack Labs is a leading team of JavaScript developers, engineers, programmers, coders, and architects. Uber, Siemens, and hundreds of other companies have chosen us for their mission-critical JavaScript development projects.

Hire Our Elite javascript Developers Now
What's included

We’ll review your code base and provide a report that includes quality scores for the following:

  • Test suite and test coverage
  • Code quality, including a CodeClimate report
  • How soon can FullStack start on my project?
  • Dependencies
  • Error and performance monitoring
  • Documentation
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Trusted By:
UberSiemensEricssonNFIBEkso BionicsCalifornia

Some of our expert JavaScript Developers.

By combining USA and Canada technical leads and project managers with Senior Developers in Latin America, we offer clients the quality, security, and convenience of onshore development paired with the cost savings of nearshore development.
Roberto Sawamura
Senior Software Engineer
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Latin America
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 Years of Experience

Senior Software Engineer, Roberto Sawamura, Latin America

Daniel Roma
Senior Software Engineer
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Latin America
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 Years of Experience

I became a developer not only to learn how computers work but also how to use them to build new things. This led me first to understand and work on the hardware, and after a few jobs in IT positions, I switched to software development to get the full picture.

Shawn Cheng
Software Architect
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 Years of Experience

FullStack Labs, Senior Software Engineer‍

Pablo Cordero
Software Architect
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Latin America
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 Years of Experience

Senior Software Engineer, Ruby on Rails Developer

Mariano Genovese
Senior Software Engineer
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Latin America
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 Years of Experience

At FullStack Labs, I write quality code that takes into account all the intrinsic aspects of a project, using React, Node.js, and more.

Ben Carle
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 Years of Experience

As the CIO of FullStack Labs I'm directly responsible for managing and contributing to our most critical client projects. I'm a senior software engineer with 15 years of experience building complex custom software and leading development teams.

Client Testimonials

We really appreciate FullStack’s expertise, and understanding of best practices, for React.js. Their team really is working at the bleeding edge of the technology. After implementing their recommendations we’ve been able to increase automation and decrease labor by 50% in our AR department, freeing up our people for more productive uses.

It’s not easy to get 5 stars from me but you guys have been great! You show up on time, you finish within the schedule. We’re doing accounting and financial systems which means that you have to learn the business side of it. It’s not only software, you have to understand the workflow. Our experience has been amazing.

- George Grant -
Director of IT, The Coding Network

Working with FullStack Labs (Gisselle and Charly) has been one of, if not THE, best work experiences I’ve had in my life - and I’ve built a lot of stuff in my 70+ years.

- Bill Estberg -
President, chill-n-go

How to Hire JavaScript Developers Through FullStack Labs

  • 1. Talk to us!

    We will work with you to understand your technical needs, team dynamics, and goals.

  • 2. Meet our available talent

    We’ll send you FullStack JavasScript developers that match your technical requirements, with links to their FullStack profile page which outlines their work experience and technical abilities, as well as their FullStack technical summary page, which includes a 60 minute video of the developer completing FullStack’s coding challenge, and a plethora of other technical information from their interview with us.

  • 3. 14 Day Risk-free trial

    Start the engagement. Work with your new JavaScript developers for a trial period, ensuring they're the right fit.

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Engagement Models for JavaScript Projects

New JavaScript Apps

We design and build greenfield apps of all shapes and sizes using JavaScript combined with a Python, Node, or Ruby on Rails backend.

Existing JavaScript Apps

Have a legacy JavaScript app? We’re here to help. From debugging and maintenance to feature development and DevOps, we'll tailor a development plan to meet your needs.

JavaScript Team Augmentation

Need to add a JavaScript developer to your existing team? We'll seamlessly integrate as many developers as needed, to help you go faster and level up your team's skills.

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FullStack Labs is proudly remote.

We have an ever growing team of incredible people currently located in these countries.
Meet our Leadership Team
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Meet our Leadership Team

Our Clients Love Us, And You Will Too.

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Let's Talk!

We’d love to learn more about your project.
Engagements start at $75,000.

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Essential Technical JavaScript Interview Questions

FullStack Labs is a leading team of JavaScript developers, engineers, programmers, coders, and architects. Uber, Siemens, and hundreds of other companies have chosen us for their mission-critical software development projects. JavaScript is a crucial tool to develop your project, here are a few JavaScript Interview Questions you can use to screen your JavaScript candidates:

Q: What is the output of console.log([, , ,].length) ?



Q: What is an “own property”?


It is a property directly assigned to the object instead of only being accessible from the object's prototype.

Q: Provide examples of non-boolean values that will coerce to a boolean one.


When any of the following values are coerced to a boolean, they will evaluate as “false”.

"""" // empty string
0, -0, NaN // 0 or invalid number
null, undefined
false // explicit false

Any other value will coerce to “true”.

42 // Number
true // explicit true boolean
[ ], [ 1, ""2"", 3 ] // arrays empty or with values
{ }, { a: 42 } // objects empty or with properties
function foo() { .. } // functions

Q: Explain what is Hoisting.


A way of thinking about hoisting suggests that variable and function declarations are physically moved to the top of your code but they aren’t actually moving. They are put into memory during the compile phase.


console.log(num); // Returns undefined, as only declaration was hoisted, no initialization has happened at this stage

var num; // Declaration
num = 6; // Initialization

Initializations using let and const are also not hoisted. 

// Example with let:
a = 1; // initialization.
let a; // Throws ReferenceError: Cannot access 'a' before initialization

// Example with const:
a = 1; // initialization.
const a; // Throws SyntaxError: Missing initializer in const declaration

Q: What are the benefits to use code transpilation, like babel, in a JavaScript project?


The code transpilation allows us to use the modern JavaScript language features provided by ECMA association without the need to wait for browser support for that features. Increasing the productivity with the language and following the javascript community best patterns.

Q: Explain what can we improve in the following code snippet:
let movieCatalog = [];
let tvShowCatalog = [];
const providers = ['netflix', 'amazon', 'hbo'];
for (let providerIndex = 0; providerIndex < providers.length; providerIndex++) {
  const providerMovies = await this.getProviderMovies(providers[providerIndex]);
  const providerTvShows = await this.getProviderTvShows(providers[providerIndex]);
  movieCatalog = [...movieCatalog, ...providerMovies];
  tvShowCatalog = [...tvShowCatalog, ...providerTvShows];


This question can have different correct answers. What we could do, for example, is:

  • Use providers.forEach instead of the old style ""for loop"".
  • Since we cannot use ""await"" inside a forEach, we can push the promises in an array and then use ""Promisse.all"", so one promise doesn't need to wait the other and then the answer will be faster.
let movieCatalogPromises = [];
let tvShowCatalogPromises = [];
const providers = ['netflix', 'amaxon', 'hbo'];

providers.forEach(provider => {

const [ movies, tvShows ] = await Promise.all([
const movieCatalog = movies.flat();
const tvShowCatalog = tvShows.flat(); 

Note: Refactor is cool. Different developers can write different versions of this code and propose refactorings. The main objective here is to understand that when handling async code we need to use the "await" carefully in order to not create performance issues.

Q: What are cookies, why are useful, and how you use them?


Cookies are small data stored on a user's computer that can be accessed by the browser.

Cookies Can be used to remember important information that improves user experience, such as let websites remember user's sessions, save shopping carts, and more.

To create a cookie you can do this:

`document.cookie = ""fsbcookie=wehaveelitejsdevelopers""`

And retrieve it like this:

`var fsbcookie =  document.cookie`

Important: `document.cookie` is a string that can contain a lot of key pairs, so you need to process the string to get the values you want.

Q: Explain what is class inheritance and give a short example.


Class inheritance is a good way to reuse code, we have to use the `extend` keyword to create a class inheritance.

class Client {
  constructor(name) {
    this.clientName = name;
  sayClientName() {
    return 'My name is ' + this.clientName;

class Project extends Client {
  constructor(clientName, companyName) {
    this.companyName = companyName;
  show() {
    return this.sayClientName() + ', and I decided to work with ' + this.companyName;

let myProject = new Project(""Paul"", ""FullStack Labs"");
=> My name is Paul, and I decided to work with FullStack Labs