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Learn TypeScript

A free, interactive TypeScript course built on top of JavaScript. You write TS on every lesson - type annotations, interfaces, generics, unions, narrowing - with AI hints when you get stuck and a certificate when you finish. Part of the wider JavaScript journey, so the JS context that makes TypeScript click is right there.

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View syllabusIntroduction To TypeScript playground

2,790+ codders enrolled

73 lessons67 challenges438 quiz questions

Syllabus

1 sections2 projects73 lessons67 challenges438 quiz questions

This section is part of the JavaScript Journey. The full syllabus has more sections: click any preview below to view it on the Journey page.

  1. Section 1Fundamentals77 lessons
  2. Section 2Logic & Flow65 lessons
  3. Section 3

    Introduction To TypeScript

    Start sectionStartExpandCollapse    Introduction to typescript after learned about javascript73 lessons73 challenges438 questions2 projects

    Getting Started with TS

    5 lessons332

    Core Types

    7 lessons1248

    Data Structure: Arrays & Tuple

    9 lessons862

    Working with Functions

    8 lessons855

    Types: Aliases, Unions & Inter

    7 lessons751

    Typing Objects and Interfaces

    8 lessons757

    Project: A Simple Task List

    6 lessons68

    Enums

    6 lessons638

    Generics: A First Look

    6 lessons537

    Project: Inventory Management

    5 lessons58

    Advanced Topics

    6 lessons642
  4. Section 4Object Oriented Programming56 lessons
View the full JavaScript Journey syllabus
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1const greeting = "Hello, Coddy!"
2function sayHi(name) {
3    return greeting + " " + name
4}
5
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Intro to Variables
Audio

A variable is a named container that stores a value you can reference later in your program.

In Python, you create one by writing the name, an equals sign, then the value you want to store.

The value can change over time. Reassigning the name simply points it to a new value.

1xSarah

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This certifies thatJohn Doehas successfully completed
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DateJan 2026
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Why learn TypeScript with Coddy

  • Write TypeScript in your browser. No tsc install, no editor setup, no tsconfig.json to wrangle. The editor and output sit side-by-side so you see what each type does instantly.
  • Modern TypeScript: type annotations, interfaces, generics, union and intersection types, narrowing, utility types, and how TS layers on top of plain JavaScript without changing what runs at runtime.
  • AI hints help you read TypeScript errors - the famously long ones - without spoiling the fix, so you build the mental model that makes future TS code easier to write.
  • Free TypeScript certificate when you finish the section. A credible signal that you can read and write idiomatic TS, not just JavaScript with sprinkled types.

Frequently asked questions about learning TypeScript

What is TypeScript?

TypeScript is a superset of JavaScript that adds optional static typing. Valid JavaScript is valid TypeScript, but TS lets you annotate variables, function parameters, and return values with types - the compiler then catches mistakes before your code runs. At runtime, TypeScript compiles down to plain JavaScript.

Is TypeScript hard to learn?

If you're comfortable with JavaScript, the basics of TypeScript are quick to pick up - adding : string or : number to a few variables and you're already writing TS. The trickier parts (generics, conditional types, mapped types, narrowing) take longer, and this course introduces them in small steps with hands-on examples.

Do I need to know JavaScript before TypeScript?

Yes. TypeScript is JavaScript with types on top, so the language you're really learning is JS. This TypeScript section is part of the JavaScript journey for that reason - you can take the JS sections first, or jump straight to TS if you're already comfortable with modern JavaScript.

What's the difference between TypeScript and JavaScript?

JavaScript is dynamically typed - a variable can hold a string today and a number tomorrow, and you only find out at runtime. TypeScript adds a static type layer that runs at build time, catching type mismatches before the code ships. The compiled output is still plain JavaScript, so it runs anywhere JS does.

Can I learn TypeScript online for free?

Yes. The interactive TypeScript section is free - full lessons, coding exercises, quizzes, and a certificate. The editor runs in your browser with the TS compiler built in, so you don't need to install tsc, Node, or any tooling to start writing TypeScript.

Do I get a certificate after the TypeScript course?

Yes. Finishing the TypeScript section gives you a free certificate of completion you can share on LinkedIn or include on your resume. A verifiable signal that you've worked through structured, hands-on TypeScript material, not just watched tutorials.

Learning paths that include this course

This course is one step of a longer path: several courses in the order a mentor would teach them, each with its own free certificate.

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