Improve entries functions

package.json

@@ -44,10 +44,9 @@
     "sinon": "^7.3.2",
     "ts-node": "^8.10.2",
     "typedoc": "^0.17.0-3",
+    "ts-expect": "^1.1.0",
     "typescript": "3.9",
     "webpack": "^4.37.0"
   },
-  "dependencies": {
-    "ts-expect": "^1.1.0"
-  }
+  "dependencies": {}
 }

src/entries/index.ts

@@ -1,6 +1,7 @@
-export type Entry<Key, Value> = [Key, Value]
-
-export type Entries<Key, Value> = Entry<Key, Value>[]
+export interface Entries<Input extends { [key: string]: any }>
+  extends Array<
+    [keyof Input, Input extends { [key: string]: infer Value } ? Value : never]
+  > {}
 
 /**
  * Creates an array of arrays where the first element is the key and second is the value.
@@ -10,11 +11,11 @@ export type Entries<Key, Value> = Entry<Key, Value>[]
  *
  * @public
  */
-export default function entries<Key extends string | number, Value>(
-  object: { [key in Key]: Value }
-): Entries<Key, Value> {
-  return (Object.keys(object) as Key[]).reduce<Entries<Key, Value>>(
+export default function entries<Input extends { [key: string]: any }>(
+  object: Input
+): Entries<Input> {
+  return Object.keys(object).reduce<[string, any][]>(
     (acc, key) => acc.concat([[key, object[key]]]),
     []
-  )
+  ) as Entries<Input>
 }

src/entries/test.ts

@@ -1,5 +1,6 @@
 import assert from 'assert'
 import entries from '.'
+import { expectType } from 'ts-expect'
 
 describe('entries', () => {
   const object = {
@@ -10,6 +11,7 @@ describe('entries', () => {
 
   it('returns entries array', () => {
     const result = entries(object)
+    expectType<number | string | { d: any[] }>(result[0][1])
     assert.deepEqual(result, [
       ['2', 3],
       ['a', 'B'],

src/fromEntries/index.ts

@@ -1,3 +1,5 @@
+import type { Entries } from '../entries'
+
 /**
  * Returns an object composed from entries, an array of [key, value].
  *
@@ -7,20 +9,31 @@
  * @category Array
  * @public
  */
-export default function fromEntries<
-  Key extends string | number,
-  Value,
-  Entry extends [Key, Value],
-  ReturnType extends { [key: string]: Value }
->(array: Entry[]): ReturnType {
-<<<<<<< HEAD
-  return array.reduce((acc, [key, value]) => {
-    acc[key] = value as ReturnType[typeof key]
-=======
-  return array.reduce((acc, cur) => {
-    //@ts-ignore
-    acc[cur[0]] = cur[1]
->>>>>>> Add category tag
+export default function fromEntries<Input>(array: Entries<Input>): Input
+
+/**
+ * Returns an object composed from entries, an array of [key, value].
+ *
+ * @param array - The entries, an array of [key, value]
+ * @returns an object composed from the entries
+ *
+ * @category Array
+ * @public
+ */
+export default function fromEntries<Entries extends [string | number, any][]>(
+  array: Entries
+): Entries extends [string | number, infer Value][]
+  ? { [key: string]: Value }
+  : never
+
+/**
+ * @internal
+ */
+export default function fromEntries(
+  array: [any, any][]
+): { [key: string]: any } {
+  return array.reduce<{ [key: string]: any }>((acc, [key, value]) => {
+    acc[key] = value
     return acc
-  }, {} as Partial<ReturnType>) as ReturnType
+  }, {})
 }

src/fromEntries/test.ts

@@ -1,5 +1,7 @@
 import assert from 'assert'
 import fromEntries from '.'
+import entries from '../entries'
+import { expectType } from 'ts-expect'
 
 describe('fromEntries', function () {
   it('returns an object from array', function () {
@@ -8,9 +10,18 @@ describe('fromEntries', function () {
       ['b', 'c'],
       [2, { d: 3 }],
     ])
+    expectType<{ [key: string]: string | number | { d: number } }>(result)
     assert.deepEqual(result, { a: 1, b: 'c', '2': { d: 3 } })
   })
 
+  it('allows to restore entries result', () => {
+    type User = { firstName: string; lastName?: string; age: number }
+    const user: User = { firstName: 'Sasha', age: 33 }
+    const result = entries(user)
+    const restoredUser = fromEntries(result)
+    expectType<User>(restoredUser)
+  })
+
   it('returns an empty object if the array is empty', () => {
     assert.deepEqual(fromEntries([]), {})
   })