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8 questions on Generics. Pass 70% to clear the chapter.

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TS Generics — Chapter Quiz

Eight questions on generic functions, constraints, classes, and patterns.

0/ 9

Question 1
1
What problem do generics solve?
AThey make code fasterBThey let one function/class work for many types without losing type infoCThey replace inheritanceDThey eliminate runtime errors
Generics let you write code that works over a range of types while preserving the actual type through inputs and outputs.
Question 2
2
What is the inferred return type of identity('hi')?
```
function identity<T>(x: T): T {
  return x;
}

const r = identity("hi");
```
AstringB"hi"CTDany
String literal arguments infer to their literal type when passed to a generic — so T is "hi".
Question 3
3
How do you constrain a generic to "must have a length property"?
A<T extends { length: number }>B<T : { length: number }>C<T implements Length>D<T where length>
T extends { length: number } restricts T to types that include a numeric length property.
Question 4
4
Type parameters can have default values like function parameters.
TTrueFFalse
<T = string> provides a default. Callers can omit the argument and the default is used.
Question 5
5
Which of these is a generic interface declaration?
Ainterface Box { value: T }Binterface Box<T> { value: T }Cinterface<T> Box { value: T }Dgeneric interface Box { value: T }
Type parameters go in angle brackets after the interface name.
Question 6
6
A type that references itself is called a ___ type.
Recursive types reference themselves — useful for trees, JSON, and other nested structures.
Question 7
7
Which of these are valid generic class signatures?
Select all that apply.
Aclass Stack<T> { ... }Bclass Pair<A, B> { ... }Cclass List<T extends object> { ... }Dclass<T> Box { ... }
Type parameters always come *after* the class name, in angle brackets. Multiple params and constraints are both allowed.
Question 8
8
Why might you use multiple type parameters like <K, V>?
APerformanceBTo express that key and value types are related but distinctCIt is requiredDYou cannot use one parameter for both
Map-like structures need separate type parameters for keys and values — they're related (paired) but generally different types.