Default Props
Default Props

This module looks at static versions in React, Props, and Mock Components to use when testing an application.

Learning Objectives 

The objectives of this module are to provide you with an understanding of: 

  • How to be able to build a static version of an application
  • How to use Props in components
  • How to be able to test Component snapshots and Components with props
  • How to be able to Mock components when testing

Intended Audience  

This Learning Path is aimed at all who wish to learn how to use the ReactJS framework.  

Prerequisites of the Course 

It is essential you understand the face of contemporary web development to attend this course. We insist upon JavaScript experience, along with good HTML and CSS skills. 


We welcome all feedback and suggestions - please contact us at to let us know what you think. 


Some components may not need props to be supplied every time they are used, as the default value may be sufficient in many cases. Props are immutable and must be supplied when a component is rendered. So how can we get default values? Default Props is the answer. If appropriate, we can supply values for each prop that should be received by the component, ensuring that it will work and render correctly, even if all the values are not supplied by the rendering parent. 

Here we have a component that expects to receive headerText, contentText, and contentText2 as props. We're going to supply headerText and contentText with default values. To give a component default props, we just need to add a default props subject to it. Inside the object, we add keys of all the props that we want to have a default value, and then supply a value. You can see that if a prop is not supplied, and a default value is available, that default value is used. If a value is supplied by the parent, as in the case of headerText, then that value is used. 

Props that are not supplied and do not have a value will fail silently if they are part of a JSX expression or if they can be used as a falsy value in a JavaScript expression. Otherwise normal JavaScript errors will be shown. As we are trying to call a substring formation on contentText2 here, which is undefined, we will get an unknown type error, as you can see in the browser console on the right hand side of the window.


About the Author
Learning Paths

Ed is an Outstanding Trainer in Software Development, with a passion for technology and its uses and holding more than 10 years’ experience.

Previous roles have included being a Delivery Manager, Trainer, ICT teacher, and Head of Department. Ed continues to develop existing and new courses, primarily in web design using: PHP, JavaScript, HTML, CSS, SQL, and OOP (Java), Programming Foundations (Python), and DevOps (Git, CI/CD, etc). Ed describes himself as practically minded, a quick learner, and a problem solver who pays great attention to detail. 

Ed’s specialist area is training in Emerging Technologies, within Web Development. Ed mainly delivers courses in JavaScript covering vanilla JS, ES2015+, TypeScript, Angular, and React (the latter is authored by Ed) and has delivered on behalf of Google for PWAs. Ed has also developed a new suite of PHP courses and has extensive experience with HTML/CSS and MySQL. 

Ed is responsible for delivering QA’s Programming Foundations course using the Eclipse IDE. His skillset extends into the DevOps sphere, where he is able to deliver courses based around Agile/Scrum practices, version control, and CI/CD.

Covered Topics