TypeScript Playground
In this page:
Writing TypeScript in the Playground
The Playground provides a browser-based editor for entering TypeScript code and instantly seeing the compiler's output, with zero setup. It's especially useful for beginners because experiments can be tried out immediately, without creating a local project or installing anything.
Example: Writing TypeScript in the Playground
// Paste into the online Playground - no setup required
let city: string = "Mumbai";
console.log(city);Viewing JavaScript Output
One of the Playground's most useful features is a side-by-side panel showing exactly how your TypeScript source is transformed into plain JavaScript. This makes it concrete that type annotations are a development-time-only feature, since they're stripped out and never appear in the emitted JavaScript.
Example: Viewing JavaScript Output
let count: number = 5;
console.log(count);
// Playground's right panel shows this compiled to: let count = 5; console.log(count);Testing Type Errors
The Playground surfaces the TypeScript compiler's diagnostics live as you type, making it a great space to experiment with the type system by intentionally writing incorrect types. Seeing exactly how and why the compiler objects builds real intuition for how the type checker reasons about your code.
Example: Testing Type Errors
let age: number = 25;
// age = "twenty"; // Playground highlights this as a type error live
console.log(age);Experimenting with Compiler Options
The Playground exposes controls for experimenting with compiler settings like target and strict without ever touching a tsconfig.json file. Toggling these options and watching both the diagnostics and the generated JavaScript change helps you understand what each setting actually controls.
Example: Experimenting with Compiler Options
// Playground sidebar toggle: target = ES5, strict = true
let value: number = 10;
console.log(value);Learning Through Experiments
Because you can change a small piece of code and immediately see both the compiler diagnostics and the generated JavaScript update, the Playground is an unusually fast feedback loop for learning. It's a convenient place to test unfamiliar TypeScript syntax before committing it to a real project.
Example: Learning Through Experiments
let x: number = 2;
let y: number = 3;
console.log(x + y);
// Change a type above and watch diagnostics/output update instantlyChapter Quiz — Complete all 7 topics to unlock
0/7 topics done
Complete these topics first: