Type Assertion

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Typescript: Zero to Hero
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This module will introduce you to Simple Types in TypeScript. You’ll learn about Arrays, Tuples, and Type Assertion, too.

Learning Objectives

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

  • What Simple Types are
  • How to use Arrays
  • How to use Tuples
  • How to use Type Assertion

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 qa.elearningadmin@qa.com to let us know what you think.


Sometimes as developers, we need to override the compiler errors. This is usually when an entity is more specific than its current type suggests. And we need access to its specific types, properties or functions. TypeScript provides us with two syntaxes to do this. The first is angle-bracket syntax. In this example, we have defined thing as any. Provided a value of type string. Unless we tell TypeScript, that thing is a string, it will not let us have access to properties and functions associated with the string type like length. Instead giving us an error. To do this, replace the variable or object and property in parentheses, and we put the type we wish, to assert on it in angle brackets before it. After the closing parentheses, we access the property or function. The second and probably the most common way to do type assertion, is the as-syntax. It follows the same pattern but uses the variable name followed by, as. And then the type to assert. If you use TypeScript in React, you have to use the second method. That now rounds up the module on types and their syntax. Don't forget to get some practice using the labs.


Simple Types: An Introduction - Arrays - Tuples - Any and Unknown - Null and Unidentified - Function Arguments and Return Types - Enums

About the Author
Learning paths6

An outstanding trainer in software development with more than 15 years experience as a Corporate and Apprentice Trainer, ICT Teacher and Head of Department, with a passion for technology and its uses. Continuing to develop existing and new skills and courses, primarily in web design using PHP, JavaScript, HTML, CSS and SQL but also OOP (Java), programming foundations (Using Python), DevOps (Git, CI/CD, etc) and Agile/Scrum. Practically minded, a quick learner and a problem solver with an attention to detail to ensure high quality outcomes.

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