Hire Top Freelance Javascript Developers with Ultragenius

Ultragenius is a marketplace for top software developers, engineers, programmers, coders, architects, and consultants. Top start-ups and companies choose developers from Ultragenius platform for their critical software projects.
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Javascript Developer

Rishabh is a software engineer having 7+ years of experience in designing front-end web applications and is expert in web development.

Expert in






10 Years


Full Time


Javascript Freelancer

Mahesh is a software engineer having 3+ years of experience in developing both client-side and server-side web applications using Javascript.

Expert in






10 Years


Full Time


Part-time Javascript Freelancer

John is a software engineer having 10+ years of experience developing server-side web applications using Javascript, Express.js, Node.js, and MongoDB.

Expert in






10 Years


Full Time

Hire top talented freelance Javascript developers with Ultragenius

Javascript is a widely-used unifying language of whole web application development. It is used on both client-side and server-side. Javascript provides optimal user-experience across various browsers, devices, and operating system. 

What Ultragenius offers?

Hire full stack Javascript Developers through Ultragenius in 4 easy steps

Tell us the skills you need

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We find the best talent for you

Get the list of pre-vetted candidates in days.

Schedule the interviews

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Start working with Ultragenius with a 1-week trial period.

Our Happy Clients

UltraGenius is the best remote talent network to meet with brilliant developers who are most talented and skilled in the technical field. UltraGenius provides the most fit developers who not only match our job requirements but also our company's culture and working environment.
Once you are part of UltraGenius, you don't have to look for another platform which can find the top skilled freelance developers with same effort as UltraGenius. UltraGenius's vetting tests and assessments are unmatchable and provides the perfect match for the job role.
Our company is thankful to UltraGenius wholeheartedly. UltraGenius's pace of finding the top 1% freelance developers is unmatchable. Not only UltraGenius developers are the ones who match our job requirements but also the best fit to our company's working culture .
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Want to hire freelance Javascript developers on your own? Here are the skills you must look for while hiring a Javascript developer

Hiring freelance Javascript developers might be an intricate task for you if you are a non-technical manager. Today, Javascript is one of the widely used language in developing both client-side and server-side in applications, and hiring the most skilled freelance Javascript developers among thousands of developers is a challenging task for anyone. So, Ultragenius is here to assist you while recruiting the top talented freelance Javascript developers on your own. Ultragenius understands your job requirements and gets you only the top developers who have in-depth knowledge of software development.

The following skills you must look for while hiring a freelance Javascript developer – 

Steadfast knowledge of HTML and CSS

HTML (Hypertext Markup Language) and CSS (Cascading Style Sheets) are the two core technologies used to design a web page. You must hire such a developer who has practiced and worked deeply with these technologies. Knowledge of Flexbox and CSS Grid, in addition to Bootstrap, Semantic and Structural Styling, and Foundation is a must to a Javascript developer. Along with this, the developer should be well-versed in Javascript libraries especially jQuery and CSS grid systems. 

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Javascript fundamentals + ES6

Javascript is most widely used language in developing dynamic web applications and helps a developer integrate back-end with the front-end easily. The freelance Javascript developer must be clear with the fundamental concepts of Javascript language. ECMAScript 6 (or ES6) is the current version of ECMAScript and is widely used by developers up to a large extent. The freelance Javascript developers must be familiar with these ES6 skills –  

  • Arrow functions
  • Blocked scope constructors let and const
  • Advanced object literals
  • Template literals
  • Multi-line strings
  • Modules
  • Module loaders
  • Binary and octal literals
  • Reflect API
  • Proxies
  • Classes
  • Destructuring assignment

CSS Pre-processors and Frameworks

A CSS pre-processor is a program that extends the functionality of CSS and compiles it into regular CSS. SASS, PostCSS, SCSS, and LESS are the extensions of regular CSS and developers use them for useful functions such as math functions, color manipulation, to write better inline documentation, to easily integrate CSS tools and CSS codebase, and much more. It makes developers write lines of code in very less time because of its in-built functionalities.

You must check the freelance Javascript developer’s knowledge of Bootstrap and Material UI, as these components enable easier and faster web development.

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CSS in Javascript allows a developer to embed CSS inside Javascript and is used widely for large-scale projects while creating a single-page application built of different components. You don’t have to keep multiple CSS files as styles are bundled within their own components. More functionalities are added to CSS like unit testing, automatic vendoring, and nesting. It achieves better performance as CSS-in-JS only loads styles that are being used currently.

Experienced in working with Version Control System (VCS)

Freelance Javascript developers must have a very good knowledge of version control systems, like Git, SVN, TFS, and Mercurial. Mostly, developers use Git for their work. It is the version control system that helps the team in collaborating and organizing your code, maintain the frequent changes that occur in the code. Git helps in reviewing the old codes and compares them with the newly updated code, pulling the code from their repository, and managing the commit history.

Along with this, the freelance Javascript developer must know how to use add, push, pull, and commit commands, branching, and merging as it allows developers to work independently on the code.

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Excellent understanding of testing frameworks and tools

Rising quick-deployment needs during the development phase, testing has become an  important skill for Javascript developers. Therefore, developers should know about Jest, Enzyme, Mocha, Chai, AVA, and Tape for unit testing.

For end-to-end testing, they must know about Selenium, Webdriver, Cucumber.js, Nightwatch.js, Cypress, and Puppeteer.

For integration testing, they must know about Karma.

Hands-on knowledge with Functional Programming

Functional programming is a paradigm of building software by composing pure functions without mutating state and data. Javascript uses a mix paradigm of programming including functional, procedural, and object-oriented paradigm. Ask developers about pure functions, their usages, and advantages. Functional programming comes under the “Declarative Paradigm” in which the program logic is written without explicitly describing the flow control.

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Knowledge of Front-end frameworks and libraries

Familiarity with at least one of the front-end frameworks is a must for any Javascript developer like React.js or Angular.js. These front-end frameworks are greatly required in today’s market. React is popular for its faster development of Single Page Applications while Angular uses interpolation, dependency injection, and eliminates coding mistakes by using the strongly typed Typescript that resolves many challenges faced by the developers.

Experience in Writing Cross-Browser compatible code

You must hire developers who can write the code that is compatible to run on any browser platform like Mozilla, Chrome, Internet Explorer. Javascript supports cross-browser compatibility to its web applications.

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Well versed in Typescript

Typescript includes strong typing which means that each expression has a data type that is determined at the compile-time and only operations designed for that data type are allowed.  Typescript specifies the variables and functions that were intended to be used at the compile time only, so you must check the developer’s knowledge of Typescript while hiring a freelance Javascript developer.


Node.js is a must know skill for any Javascript developer. .It is a run-time environment that enables back-end Javascript development.

A Javascript developer can build dynamic web applications using without writing a complex code. Node.js works on an asynchronous paradigm for handling the data between client and server and is able to serve multiple threads at a single time.

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Experience with web markup and UI, UX Concepts

The developer must have a firm understanding of element positioning, displaying the elements, and making components interactive, semantic markup, and other related UX Concepts so they can design the product with the best quality. The developer must be experienced in developing visual effects in presentational markup. For, example – How the heading appears, making text larger and putting weight to it, and giving which color to it, and which markup can include captions, bind columns, and row headings to table cells. 


Most important skill for JS developer – For a Javascript developer, jQuery is the most important library which is used in developing Javascript applications. Among the top 10 million websites that operate today, 77.8% of them use jQuery because jQuery functions on top of Javascript. It simplifies HTML document traversing and manipulation, event handling,  CSS animation, and Asynchronous Javascript and XML (AJAX) interactions for rapid application development.

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Proficient in writing optimized and readable code

You must hire the developers based on their ability to write clean and optimized code that is understandable by all the team members, and is scalable.

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Connect with the top 1% freelance Javascript developers of the world at the lowest prices

Almost everyone prefers to use Javascript for building optimized web applications  because of its flexibility on both client-side and server-side and extraordinary ability to create rich User Interfaces.  But recruiting the best freelance Javascript developers is not an easy task when a large no. of Javascript freelancers are competing to grab the job opportunities.

Top Interview Questions to ask while hiring a freelance Javascript developer

Javascript is loosely or dynamically typed language. In loosely typed language, the data type of the variable is checked at run-time and not like strongly typed language where the data type of the variable is checked at the compile-time only. Variables in Javascript don’t hold any fixed data type. A variable assigned a string type can be converted into a string type and vice versa. For example var str = “Hello World !!!”, var str = 12345.

In Javascript, keyword ‘this’ behaves differently based on how a function is called at run time. It can be assigned during execution and its value may be different each time when the function is invoked. The value of ‘this’ is different each type the function is invoked. ECMAscript 5 introduced the bind() function to set the function’s ‘this’ value, regardless of how it is called. ECMAscript2015 introduced the concept of “arrow functions” which don’t provide ‘this’ binding their own but it gets the ‘this’ value of the enclosing text context.


Outside any function, ‘this’ represents any global object regardless of strict mode. 

In Javascript, pass by value refers to the function which is called directly by passing the variable value as argument. Changing the function arguments does not impact the variable passed from outside the function.


In pass by reference, function is called by passing the variable’s address as function argument. Here, changing the function arguments impact the variable passed from outside the function. 

Scope determines the accessibility of the variables, functions, and objects within the Javascript program during runtime. There are four types of scope in Javascript - 

  • Global Scope
  • Block Scope
  • Function Scope
  • Local Scope


  • Global Scope  - A variable declared outside any function becomes global and can be accessed from anywhere in the Javascript program. 
  • Block Scope - The two keywords ‘let’ and ‘const’ introduced by ES6 provide block scope, and variables declared inside {....} are accessed within this block only.
  • Function Scope - Variables defined inside a function are not accessible outside the function.
  • Local Scope - Local variables have their scope limited to the functions i.e., created when the function starts and deleted when the function ends. 

Scope chain determines the scope for a given function. Each function that is defined  has its own nested scope and the nested function (function defined inside function) has a local scope which is linked to its outside function, this is called scope chain.

When the bind() method is invoked, the JS engine creates a new function and binds the variable as its ‘this’ variable. The call() method invokes a function by explicitly specifying what ‘this’ should point to within the calling function. The difference between bind() and call() is that call() accepts the additional parameters also, and does not make the function’s copy on which it is invoked.


The apply() method works the same as call() method but the only difference is apply() takes an array of parameters to be passed within it while the call() method expects the parameters to be passed individually.

Hoisting in Javascript is the default behavior in which a variable or function is moved to the top of the current scope (scope refers to a script or function) and can be used before declaring them.

For example, console.log(test);

var test;

works as

var test;

console.log(test); The output in both the cases is undefined. 

Currying is the technique of breaking down a function that takes multiple arguments into the function series that take only one argument. 

For example,



return a+b;


 can be written as 

function add (a){ 

return function (b); 

return a+b;



Javascript is synchronous in nature as it holds another requests while executing a request. When you run a block of code in Javascript, no other block will be executed on that page at the same time. However, it implements asynchronous handling in its event like in the form of callbacks feature, async/await, and promises

jQuery is a small, fast, and cross-browser compatible library that simplifies tasks like HTML traversal and DOM Manipulation, AJAX calls, JSON parsing, CSS effects and animations, provides extensibility through plugins, and many more.  jQuery binds multiple lines of code into functions that can be invoked only writing one line of code.

Frequently Asked Questions

Ultragenius is one of the leading platforms for hiring remote talent and connecting freelance and part-time developers with Silicon Valley businesses. We focus on finding the best talents who will perform extremely well and will be easily integrated into your teams. We filter out only the top 1% most skilled freelance developers among the 20K+ developers who have applied on our platform. Candidates have to prove their self-reported experience by giving Ultragenius’ s skill tests.

Ultragenius first tests the developer’s skill set by conducting a two and half hour hiring test. Our hiring test judges a candidate on all aspects like aptitude, case study analysis, verbal and reasoning, coding questions based on data structures and algorithms, software engineering, system design, and more. Then, there is another round for the candidates who are selected from this round called “Higher-level Assessment Skill Test”, which is a video round that deeply analyzes freelance developers’ major skills and asks questions about the projects they have worked upon.

Fill up the form which is on every hiring freelancers’ page and we will inform you once we select the top 1% freelance Javascript developers matching your job requirements.  After analyzing the candidates based on their resumes and two assessment tests, we provide you the feedback quickly. And if the freelancers selected by our team are fit for your job role, then we also provide the onboarding.

Ultragenius offers you only the most skilled freelance developers who are top 1% among the 20K+ freelance developers who have applied on our platform. After a rigorous selection and testing process, we sort out only the top candidates for you. You can check out Ultragenius’ s selection process for hiring freelance Javascript developers on http://www.ultragenius.club/hire-javascript-freelancer

Ultragenius provides you the best facility to hire freelancers in more than 50 skills like React, Angular, Javascript, Node, Java, Python, Magento, Ruby On Rails, Golang, PHP, WordPress, .NET, Android, iOS, DevOps, Machine Learning, and many more.

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