TypeScript -Interfaces

The course is part of this learning path

An Introduction to Interfaces

This module introduces you to Interfaces in TypeScript.

Learning Objectives

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

  • How to use Function Types
  • How to use Optionals
  • How to use Excess Property Checks
  • How to use Indexable Types
  • How Interfaces work with Classes
  • How to create Extendable Interfaces

Intended Audience

This learning path is aimed at all who wish to learn how to use TypeScript


It is essential you understand the face of contemporary web development to attend this course. You should have a good working knowledge of Javascript. Please note: Before attending this class delegates must have a Microsoft account (signing up one is free).


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


Interfaces are an important aspect of object-oriented programming. In this module, we'll investigate how to create and use interfacing TypeScript, apply inheritance to them, and understand how excess property checks are done. JavaScript follows single inheritance, so like in other languages, interfaces can be used to add extra rules to classes, but they can also be used to define the shape of objects for use in functions. An interface is like a contract. When we sign up to it, or make a class implement it, we must follow the rules of interface or face error messages. They're a bit like abstract classes, with only abstract methods and properties. No concrete implementation or data is held within an interface. Interfaces are duck typed. The compiler simply checks that we have at least the required members. The argument to the function need not be an instance or match the interface exactly. It just needs to satisfy its requirements, and it's important to remember that interfaces are just more syntactic sugar.


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