{"@context":"https://schema.org","@type":"Quiz","name":"TypeScript Generics","educationalLevel":"intermediate","assesses":"TypeScript","educationalAlignment":[{"@type":"AlignmentObject","alignmentType":"educationalSubject","targetName":"Computer Science"}],"about":{"@type":"Thing","name":"TypeScript"},"description":"A 10 question quiz covering TypeScript. Answers are multiple choice.","hasPart":[{"@type":"Question","eduQuestionType":"Multiple choice","text":"What is the main purpose of generics in TypeScript?","encodingFormat":"text/markdown","suggestedAnswer":[{"@type":"Answer","position":0,"text":"To make values mutable at runtime","encodingFormat":"text/plain"},{"@type":"Answer","position":1,"text":"To write reusable code that works with many types while staying type-safe","encodingFormat":"text/plain"},{"@type":"Answer","position":2,"text":"To replace interfaces entirely","encodingFormat":"text/plain"},{"@type":"Answer","position":3,"text":"To disable strict null checks","encodingFormat":"text/plain"}],"acceptedAnswer":{"@type":"Answer","position":1,"text":"To write reusable code that works with many types while staying type-safe","encodingFormat":"text/plain"}},{"@type":"Question","eduQuestionType":"Multiple choice","text":"How do you declare a generic type parameter on a function?","encodingFormat":"text/markdown","suggestedAnswer":[{"@type":"Answer","position":0,"text":"function foo(x: T): T","encodingFormat":"text/plain"},{"@type":"Answer","position":1,"text":"function foo(x: generic): generic","encodingFormat":"text/plain"},{"@type":"Answer","position":2,"text":"generic function foo(x)","encodingFormat":"text/plain"},{"@type":"Answer","position":3,"text":"function foo(x: any)","encodingFormat":"text/plain"}],"acceptedAnswer":{"@type":"Answer","position":0,"text":"function foo(x: T): T","encodingFormat":"text/plain"}},{"@type":"Question","eduQuestionType":"Multiple choice","text":"What does `Array` express?","encodingFormat":"text/markdown","suggestedAnswer":[{"@type":"Answer","position":0,"text":"An array that may hold any type","encodingFormat":"text/plain"},{"@type":"Answer","position":1,"text":"An array whose elements are typed as strings","encodingFormat":"text/plain"},{"@type":"Answer","position":2,"text":"A tuple of exactly one string","encodingFormat":"text/plain"},{"@type":"Answer","position":3,"text":"A readonly string","encodingFormat":"text/plain"}],"acceptedAnswer":{"@type":"Answer","position":1,"text":"An array whose elements are typed as strings","encodingFormat":"text/plain"}},{"@type":"Question","eduQuestionType":"Multiple choice","text":"When you call `identity(42)` where `identity` is `(x: T) => T`, what is `T` inferred as?","encodingFormat":"text/markdown","suggestedAnswer":[{"@type":"Answer","position":0,"text":"unknown","encodingFormat":"text/plain"},{"@type":"Answer","position":1,"text":"any","encodingFormat":"text/plain"},{"@type":"Answer","position":2,"text":"number","encodingFormat":"text/plain"},{"@type":"Answer","position":3,"text":"never","encodingFormat":"text/plain"}],"acceptedAnswer":{"@type":"Answer","position":2,"text":"number","encodingFormat":"text/plain"}},{"@type":"Question","eduQuestionType":"Multiple choice","text":"What is a common reason to add a generic constraint such as ``?","encodingFormat":"text/markdown","suggestedAnswer":[{"@type":"Answer","position":0,"text":"To make `T` optional","encodingFormat":"text/plain"},{"@type":"Answer","position":1,"text":"To ensure `T` has certain properties before using them safely","encodingFormat":"text/plain"},{"@type":"Answer","position":2,"text":"To force `T` to be a primitive","encodingFormat":"text/plain"},{"@type":"Answer","position":3,"text":"To compile faster","encodingFormat":"text/plain"}],"acceptedAnswer":{"@type":"Answer","position":1,"text":"To ensure `T` has certain properties before using them safely","encodingFormat":"text/plain"}},{"@type":"Question","eduQuestionType":"Multiple choice","text":"What is `Promise` describing?","encodingFormat":"text/markdown","suggestedAnswer":[{"@type":"Answer","position":0,"text":"A function that returns a string","encodingFormat":"text/plain"},{"@type":"Answer","position":1,"text":"A Promise that should resolve to a string value","encodingFormat":"text/plain"},{"@type":"Answer","position":2,"text":"A string that might be a Promise","encodingFormat":"text/plain"},{"@type":"Answer","position":3,"text":"An error type for async code","encodingFormat":"text/plain"}],"acceptedAnswer":{"@type":"Answer","position":1,"text":"A Promise that should resolve to a string value","encodingFormat":"text/plain"}},{"@type":"Question","eduQuestionType":"Multiple choice","text":"Can a class be generic in TypeScript?","encodingFormat":"text/markdown","suggestedAnswer":[{"@type":"Answer","position":0,"text":"No, only functions can use generics","encodingFormat":"text/plain"},{"@type":"Answer","position":1,"text":"Yes, for example `class Box { value: T }`","encodingFormat":"text/plain"},{"@type":"Answer","position":2,"text":"Only if the class is abstract","encodingFormat":"text/plain"},{"@type":"Answer","position":3,"text":"Only inside `.tsx` files","encodingFormat":"text/plain"}],"acceptedAnswer":{"@type":"Answer","position":1,"text":"Yes, for example `class Box { value: T }`","encodingFormat":"text/plain"}},{"@type":"Question","eduQuestionType":"Multiple choice","text":"What happens if you use the same type parameter name in an outer and inner scope?","encodingFormat":"text/markdown","suggestedAnswer":[{"@type":"Answer","position":0,"text":"The inner parameter shadows the outer one","encodingFormat":"text/plain"},{"@type":"Answer","position":1,"text":"TypeScript merges them into one","encodingFormat":"text/plain"},{"@type":"Answer","position":2,"text":"It is always a compile error","encodingFormat":"text/plain"},{"@type":"Answer","position":3,"text":"The outer parameter is deleted","encodingFormat":"text/plain"}],"acceptedAnswer":{"@type":"Answer","position":0,"text":"The inner parameter shadows the outer one","encodingFormat":"text/plain"}},{"@type":"Question","eduQuestionType":"Multiple choice","text":"Why might you pass an explicit type argument like `createPair(1, 2)`?","encodingFormat":"text/markdown","suggestedAnswer":[{"@type":"Answer","position":0,"text":"To make the code longer","encodingFormat":"text/plain"},{"@type":"Answer","position":1,"text":"When inference would pick a wider type than you want (for example `number` vs literal types)","encodingFormat":"text/plain"},{"@type":"Answer","position":2,"text":"To avoid using `const`","encodingFormat":"text/plain"},{"@type":"Answer","position":3,"text":"To enable runtime reflection","encodingFormat":"text/plain"}],"acceptedAnswer":{"@type":"Answer","position":1,"text":"When inference would pick a wider type than you want (for example `number` vs literal types)","encodingFormat":"text/plain"}},{"@type":"Question","eduQuestionType":"Multiple choice","text":"Which statement about default generic type parameters is correct?","encodingFormat":"text/markdown","suggestedAnswer":[{"@type":"Answer","position":0,"text":"They are not supported in TypeScript","encodingFormat":"text/plain"},{"@type":"Answer","position":1,"text":"You can write `` so callers may omit `T`","encodingFormat":"text/plain"},{"@type":"Answer","position":2,"text":"They only work on interfaces, not types","encodingFormat":"text/plain"},{"@type":"Answer","position":3,"text":"They must always be `any`","encodingFormat":"text/plain"}],"acceptedAnswer":{"@type":"Answer","position":1,"text":"You can write `` so callers may omit `T`","encodingFormat":"text/plain"}}]}

TypeScript Generics Quiz

Question 1