type-challenges#18220 - Filter (type-challenges#18221)

Co-authored-by: Muhun Kim <5278201+x86chi@users.noreply.github.com>
clgingili · Nov 16, 2022 · 2044c75 · 2044c75
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diff --git a/questions/18220-medium-filter/README.md b/questions/18220-medium-filter/README.md
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+Implement the type `Filter<T, Predicate>` takes an Array `T`, primitive type or union primitive type `Predicate` and returns an Array include the elements of `Predicate`.
diff --git a/questions/18220-medium-filter/info.yml b/questions/18220-medium-filter/info.yml
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+difficulty: medium
+title: Filter
+tags: array, filter
+author:
+  github: x86chi
+  name: Muhun Kim
+
diff --git a/questions/18220-medium-filter/template.ts b/questions/18220-medium-filter/template.ts
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+type a = Filter<[0, 1, 2], 2> // expected to be [2]
+type b = Filter<[0, 1, 2], 0 | 1> // expected to be [0, 1]
+
+type Falsy = false | 0 | '' | null | undefined
+type c = Filter<[0, 1, 2], Falsy> // expected to be [0]
diff --git a/questions/18220-medium-filter/test-cases.ts b/questions/18220-medium-filter/test-cases.ts
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+import type { Equal, Expect } from '@type-challenges/utils'
+import { ExpectFalse, NotEqual } from '@type-challenges/utils'
+
+type Falsy = false | 0 | '' | null | undefined
+
+type cases = [
+  Expect<Equal<Filter<[0, 1, 2], 2>, [2]>>
+  Expect<Equal<Filter<[0, 1, 2], 0 | 1>, [0, 1]>>
+  Expect<Equal<Filter<[0, 1, 2], Falsy>, [0]>>
+]
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		Implement the type `Filter<T, Predicate>` takes an Array `T`, primitive type or union primitive type `Predicate` and returns an Array include the elements of `Predicate`.