React.js Online Test

Topics covered
  • Mounting Method
  • Render Function
  • Password Principles
  • Component Optimize
  • Default Values for Properties
  • Handling Events
  • React Facts
  • Test Duration: 35 minutes
  • No. of Questions: 12
Useful for hiring
  • React.js Developer
  • JavaScript Developer – React.js
  • Front End Developer – React.js
  • React.js Consultant
  • Fullstack Developer – React.js
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Sample Questions

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React methods and rendering

Q 1. You’re developing a web form application in ReactJS. One of the primary features that your application should have is the focus control feature of ReactJS. With this feature, you can automatically enable an input box auto-focused before it is filled. The shown below picture of the application suggests that input box on the left side is not focus controlled while the one on the right side is focus controlled. Your task is to set focus on an input box after it gets rendered.

To implement this, you have written the code given below for App component.

Few lines in the code are missing (//Write your code here). You need to complete the code.

At Blank 1: Create a ref to store a DOM element named textInput.

At Blank 2: Set focus on nameInput box.

At Blank 3: Set default value (“Focus doesn’t work here” & “Focus works here”) for the two input boxes as shown above.

At Blank 4: Use the `ref` callback to store a reference to the text input DOM - myInput.

At Blank 5: Render the App component appropriately.

Sample Script:

class App extends React.Component{


render() {

} ReactDOM.render( , document.getElementById('app'));

Components and props

Q 2. You find that all react components must act like pure functions concerning their props. How is it possible for you to get components to change their output over time in response to user actions and network responses without violating this rule?

Q 3. You are rendering a component A which in turn rendering another component B. You want the component B to hide itself even after the rendering.
What will you do to prevent the rendering of B?

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About React.js Online Test

React.js is an open-source JavaScript library used for building reusable UI components. It helps in building encapsulated components that manage their own state & then combine them to make complex UIs. React.js allows developers to create large web-applications that use data and can change over time without reloading the page. React processes only user interfaces in applications and aims primarily to provide speed, simplicity, and scalability.

Why use iMocha’s React.js online test?

React JS online test helps employers in many ways including hiring job-fit candidate within a short time span, taking unbiased employee performance appraisal decisions, reduce hassle in mass recruitment, and more. Questions on mounting method, render function, password principles, component optimize will help you to assess React JS skills of the candidate. Our React JS coding test can be taken online by candidates from anywhere in the comfort of their time zone.

The React.js skills test helps to screen the candidates who possess traits as follows: 

1.  Thorough understanding of React.js and its core principles
2.  Ability to develop user interface components and implementation using popular React.js workflows such as Flux or Redux
3.  Excellent knowledge of core web fundamentals like HTML5, JavaScript (DOM manipulation and the JavaScript object model), and CSS3
4.  Familiarity with server-side scripting knowledge and interfacing
5.  Strong experience of working with data structure libraries
6.  Use our React JS assessment test or ask us to make a custom made test that includes skill set as per your job description.

React JS online test helps recruiters and hiring managers to evaluate the expertise of candidates in creating interactive UIs using React.js. Online React.js coding test is created & validated by experienced subject matter experts (SMEs) to assess & hire React JS developer as per industry standards.
Our React.js coding test reports are quick and provide you with insightful data, which will help you to select relevant candidates for the interview. You can use our role-based access control feature to restrict system access based on the roles of individual users within the recruiting team. Features like window violation and webcam proctoring help detect cheating while candidates attempt online React.js test.

React.js skills test may contain MCQs (Multiple Choice Questions), MAQs (Multiple Answer Questions), Fill in the Blanks, Whiteboard Questions, Audio / Video Questions, LogicBox (AI-based Pseudo-Coding Platform), Coding Simulators, True or False Questions, etc.