Hire The Top 1% Freelance JavaScript Developers

JavaScript was invented around 30 years ago by Brendan Eich. Since then, many frameworks and libraries have been built on top of it. Today, it is the most widely used programming language across the world. It is supported across platforms - laptops, phones and tablets. JavaScript can be used on the client side as well as server side.

JavaScript developers are highly versatile and a great addition to your developer team. If you are looking to hire one, you’re at the right place. Below, we have put together all the details you need to know about hiring a skilled JavaScript developer.

WWe have split the sections into the following parts:
1. Let's introduce JavaScript development to you
2. Why is JavaScript development widespread?
3. What are the tools used by JavaScript developers?
4. Writing the Job Description to hire a freelance JavaScript developer
5. Interview questions for hiring a freelance JavaScript developer
- Basic Questions
- Advanced Questions
- Data Structures/Algo Questions

1. Let's introduce JavaScript development to you

• Origin Story: Brendan Eich invented JavaScript close to 30 years ago, in 1995. Initially, JavaScript was developed for Netscape 2. Later, in 1997, it became the ECMA-262 standard. Then, Mozilla worked on developing JavaScript to be used in the Firefox browser. In the same year, Internet Explorer was the first browser to support the first version of JavaScript, ECMA-262 Edition 1.


• Widely popular: According to Statista, JavaScript is the most used programming language in the world. More than 64% of all developers globally make use of this language.


• Versatility: JavaScript is a highly versatile programming language. Knowledge of JavaScript makes it easier to pick up popular front-end as well as back-end frameworks like Angular, React and NodeJS.



2. Why is JavaScript widespread?

• Completely customizable: JavaScript alone can be used in combination with HTML/CSS to build a simple, yet fully functioning application.
• Open community and standards: Having been around for so many years, the JavaScript community is huge. Clear documentation is available which makes it easy to solve challenges.



3. What are the tools used by JavaScript developers?

1. Code Editors

• Atom: Atom is a code editor with a lot of intuitive features that make writing JavaScript code easy. Developers can download a variety of plugins to improve their experience.
• Visual Studio Code: This tool includes inbuilt JS debugging, code navigation, formatting, and other useful features which make the JavaScript coding experience easy and fruitful.

2. Package Manager - npm

npm or Node Package Manager is a tool that puts modules in order so that these become easy to find and any dependency conflicts are easily managed.

3. Task Runner - Gulp

This is a cross-platform streaming task runner using which developers can automate a lot of tasks, reducing development time.

4. Module Bundler - Webpack

Webpack is a free, open-source module bundler. It bundles JavaScript files for usage in browsers. It generates a single or few files from a large number of files that are used to then run the app.

5. Code Analysis - ESLint

ESLint is a JavaScript linter that statically analyzes the written code to find any problems present in it. This helps JavaScript developers to make the code more consistent and avoid any bugs.

6. Testing - Mocha

Mocha is a simple and easy-to-use JavaScript testing framework, mainly for Node.js programs. It has features like browser support, async testing, and coverage reports.




4. Writing the Job Description to hire a freelance JavaScript developer

Given below are key points that we at Flexiple have learned through trial and error - a process of filtering through over 15,000 developers.

• No. of years of software development experience: Be specific about the technology you’re looking for and the number of years of experience needed. The number of production apps worked on can also be used as a proxy to this parameter.


• Type of products built in the past: Based on the type of product you are trying to build - social network, SAAS product, etc. - you can prioritize certain developers over others


• Industry-specific exposure: JavaScript developers who have built products in certain industries have better knowledge of the key aspects of laying the foundation for a great product. This makes prediction of possible problems easier.


• Experience working remotely: Hiring someone who has worked remotely in the past is an added benefit as they have front-hand experience of everything right from how the contracts work to communication and from timelines to deliverables.


• Strong communication: A vital thing to look at when hiring a freelancer is excellent communication skills. Since all interactions happen online, a freelancer should be able to effectively communicate to ensure a streamlined execution of all work



5. Interview questions for hiring a freelance JavaScript developer

Now that you have prepared a quality JD, it can still be tricky to evaluate the skills of your applicants. To help you with that, we have created a pool of questions that a good JavaScript developer should be comfortable with.
Note that the ability to answer these questions doesn't imply that you have a top quality candidate. But, it definitely is a big step in that direction.

To help you navigate through these questions, we’ve categorized the interview questions in 3 parts:


A. Basic concepts: Includes all basic concepts used across languages. This will give you an understanding of how strong their programming foundation is.

B. Advanced concepts: Includes all concepts that someone with higher expertise should know.

C. DS/Algorithm questions: To test the logical capability of the candidate.




A. Basic concepts

ESLint

• After setting up your project (that is running ‘npm init’), run ‘npm install eslint --save-dev’.
• After that we run ‘npx eslint --init’ this is used to generate the ‘.eslintrc.json’ file which is the config file for eslint.
• When we are generating a the config file, it asks a bunch of questions to generate it, these are what I’ve chosen:

√ How would you like to use ESLint? · style
√ What type of modules does your project use? · commonjs
√ Which framework does your project use? · none
√ Does your project use TypeScript? · No / Yes
√ Where does your code run? · node
√ How would you like to define a style for your project? · guide
√ Which style guide do you want to follow? · standard
√ What format do you want your config file to be in? · JSON 

• It might have some peer dependencies that it wants you to install - install them too.
• Now we come to using the linter. We run ‘npx eslint app.js’ (here app.js is the source js file).

const obj = {
    "prop1": {
        "ex": "ex",
        "prop2": {
            "ex": "ex"
        }
    }
}

const objCopy = JSON.parse(JSON.stringify(obj))
  
console.log(objCopy)

2:1   error  Expected indentation of 2 spaces but found 4   indent
   2:5   error  Strings must use singlequote                   quotes
   2:5   error  Unnecessarily quoted property 'prop1' found    quote-props
   3:1   error  Expected indentation of 4 spaces but found 8   indent
   3:9   error  Unnecessarily quoted property 'ex' found       quote-props
   3:9   error  Strings must use singlequote                   quotes
   3:15  error  Strings must use singlequote                   quotes
   4:1   error  Expected indentation of 4 spaces but found 8   indent
   4:9   error  Strings must use singlequote                   quotes
   4:9   error  Unnecessarily quoted property 'prop2' found    quote-props
   5:1   error  Expected indentation of 6 spaces but found 12  indent
   5:13  error  Strings must use singlequote                   quotes
   5:13  error  Unnecessarily quoted property 'ex' found       quote-props
   5:19  error  Strings must use singlequote                   quotes
   6:1   error  Expected indentation of 4 spaces but found 8   indent
   7:1   error  Expected indentation of 2 spaces but found 4   indent
  11:1   error  Trailing spaces not allowed                    no-trailing-spaces
  12:21  error  Newline required at end of file but not found  eol-last

✖ 18 problems (18 errors, 0 warnings)
  18 errors and 0 warnings potentially fixable with the `--fix` option.

const obj = {
  prop1: {
    ex: 'ex',
    prop2: {
      ex: 'ex'
    }
  }
}

const objCopy = JSON.parse(JSON.stringify(obj))

console.log(objCopy)

Difference between Cookie and Local Storage 

• Local storage does not have the concept of expiration time. So, the developer dealing with it needs to handle the expiration of tokens stored in it. Whereas, the expiration time for cookies can be set while storing the cookie and the browser handles the rest.
• Local storage is not sent with every HTTP request, like a cookie is sent. This reduces load on especially those HTTP requests which are public and do not require to use the token stored.
• The server can directly interact with cookies, whereas only the client side script can interact with local storage.
• Local storage has a much larger storage capacity of 5mb compared to 4kb of cookie. This is primarily because cookies are meant to be read by the server, whereas local storage is meant for the client side to be able to persistently store data.

Vulnerabilities

C. Data Structure/ Algorithm

var p = 2;
var q = 4;
var r = 6;
if (p > q > r)
     document.write("true");
else
    document.write("false");

The answer is False. It may look like the output can be true because 6 > 4 > 2 is true, but PHP evaluates $z > $y 
first, which returns a boolean value of 1 or true. This value (true or 1) is compared to the 
next integer in the chain, bool(1) > $z, which will result in NULL and echo “false.”

Parting thoughts on hiring a freelance JavaScript developer