Keentune
Adaptive skill practice — find your level, get sharper.

TypeScript practice

Master the type system senior interviews test
Go deep on TypeScript’s type system — generics and constraints, inference, narrowing, unions and discriminated unions, conditional and mapped types, the utility types, and the strictness rules — through real code-based questions with clear explanations. Built to take you from solid to expert and to ace the TypeScript questions in senior-engineer interviews. Part of the Developer track.
• Meets you at your level — never too easy, never too hard.
• Adapts every question to how you’re doing.
• Tracks your level over time. Skill practice, not a test.
New here? Read the TypeScript guide
A free 15-minute primer — the mental model, the mistakes beginners make, and what to practise first.
Curriculum
313 concepts across 20 chapters, from foundations through advanced practice — each one a concept the adaptive question bank can teach and test.
A. Type-system foundations
20
B. Special & top/bottom types
10
C. Assignability & compatibility
10
D. Declarations & inference
10
E. Object types
20
F. Functions
25
G. Narrowing & control-flow analysis
25
H. Assertions & operators
10
I. Generics
20
J. Type manipulation
31
K. Built-in utility types
19
L. Compiler configuration
27
M. Modules & package architecture
16
N. Classes
25
O. Enums
9
P. Iterators, generators and symbols
8
Q. Decorators
6
R. Mixins
4
S. JSX
6
T. The compiler as a program: CLI, emit and JavaScript interop
12
View the full curriculum →
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