mediumtypeof type queries
What does `BoxCtor` represent, and which expression below is therefore valid?
class Box {
value = 0;
static make() { return new Box(); }
}
type BoxCtor = typeof Box;TypeScript Essentials
Types, generics, narrowing. Write TS with confidence.
- Questions
- 10
- Tier
- Starter
- Language
- TypeScript
- Time
- ~12 min
Difficulty mix: 5 easy, 4 medium and 1 hard. The questions are drawn from the TypeScript library at the moment you start, so sitting the test twice does not give you the same paper.
What this test can pull from
44 TypeScript topics are in scope. These are the real topic labels on the questions.
- type annotations
- hand-rolled utility types
- primitive types
- ESM CJS interop
- conditional-type distribution
- control-flow analysis pitfalls
- generic constraints
- declaration merging
- excess property checks
- mapped types
- union and literal types
- infer
- inference internals
- arrays and tuples
- moduleResolution modes
- keyof and indexed access
- discriminated unions
- structural typing unsoundness
- user-defined type guards
- NoInfer and const type params
- variadic tuple types
- index signatures
- typeof type queries
- polymorphic this
- verbatimModuleSyntax isolatedModules
- satisfies operator
- interface vs type alias
- template literal types
- conditional types
- assertion functions
Questions of the kind this test asks
Six real TypeScript questions from the same pool, snippet included. The answer options and explanations are not shown here. Those come after you attempt them.
hardarrays and tuples
What is the type of x?
const arr: number[] = [1,2,3];\nconst x = arr[0]; // with noUncheckedIndexedAccesshardtemplate literal types
What is X?
type X = `${Capitalize<"foo">}Bar`;mediumprimitive types
What is the type of x?
let x = 5;hardtypeof type queries
What is the type of f?
const f = (x: number) => x + 1;hardprimitive types
What is X?
type X = string & number;Prefer to pick your own questions? Browse all TypeScript questions. See the other 10 tests.