Lesson overview · Free interview practice

TS Basics

Open the guided first pass

Learn TypeScript fundamentals and setup.

Topics in the full lesson
  • Introduction to TypeScript
  • Setting Up TypeScript
  • TypeScript vs. JavaScript
  • Basic Types and Syntax
  • Interfaces and Type Aliases
  • Classes and Inheritance
  • Generics
  • Modules and Namespaces
  • TypeScript Compiler Options
  • Best Practices
  • Exercises

Practice Problems

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TheoryEasy

TypeScript vs JavaScript

Question

What is TypeScript, and what does it add to JavaScript? Show equivalent code in each.

Take a moment to think about this before revealing the answer

Explain your reasoning or try an implementation before comparing answers.

TheoryEasy

Why TypeScript: The Value Proposition

Question

What does TypeScript give you that JavaScript doesn't? When is it NOT worth the cost?

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Explain your reasoning or try an implementation before comparing answers.

TheoryEasy

Type Erasure: TS Types Disappear at Runtime

Question

What does it mean that TypeScript "erases" types? Show what compiled output looks like and the practical consequences.

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Explain your reasoning or try an implementation before comparing answers.

TheoryMedium

Structural Type System: Types Compare by Shape

Question

What does it mean that TypeScript uses a structural type system? Contrast with nominal typing (Java, C#) and show the practical consequences.

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Explain your reasoning or try an implementation before comparing answers.

TheoryHard

TypeScript's Intentional Unsoundness

Question

Is TypeScript a sound type system? What does that mean, and where does TS deliberately accept unsoundness for ergonomic reasons?

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Explain your reasoning or try an implementation before comparing answers.

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