feat: add mapify function

benchmarks/array/mapify.bench.ts

@@ -0,0 +1,27 @@
+import * as _ from 'radashi'
+import { bench } from 'vitest'
+
+describe('mapify', () => {
+  bench('with full list and identity value function', () => {
+    const list = [
+      { id: 'a', word: 'hello' },
+      { id: 'b', word: 'bye' },
+      { id: 'c', word: 'oh' },
+      { id: 'd', word: 'hey' },
+      { id: 'e', word: 'ok' },
+    ]
+    _.mapify(
+      list,
+      x => x.id,
+      x => x,
+    )
+  })
+
+  bench('with empty list', () => {
+    _.mapify(
+      [],
+      (x: any) => x.id,
+      x => x,
+    )
+  })
+})

docs/array/mapify.mdx

@@ -0,0 +1,38 @@
+---
+title: mapify
+group: "Array"
+description: Convert an array to a map
+---
+
+## Basic usage
+
+Given an array of items, create a map with keys and values mapped by given
+functions. First argument is the array to map. The second argument is the
+function to determine the key for each item. The third argument is optional and
+determines the value for each item.
+
+```ts
+import * as _ from "radashi";
+
+const fish = [
+  {
+    name: "Marlin",
+    weight: 105,
+  },
+  {
+    name: "Bass",
+    weight: 8,
+  },
+  {
+    name: "Trout",
+    weight: 13,
+  },
+];
+
+_.mapify(fish, f => f.name); // => Map(3) {'Marlin' => { name: 'Marlin', weight: 105 }, 'Bass' => { name: 'Bass', weight: 8 }, 'Trout' => { name: 'Trout', weight: 13 }}
+_.mapify(
+  fish,
+  f => f.name,
+  f => f.weight
+); // => Map(3) { 'Marlin' => 105, 'Bass' => 8, 'Trout' => 13 }
+```

src/array/mapify.ts

@@ -0,0 +1,11 @@
+export function mapify<T, Key, Value = T>(
+  array: readonly T[],
+  getKey: (item: T) => Key,
+  getValue: (item: T) => Value = item => item as unknown as Value,
+): Map<Key, Value> {
+  const map: Map<Key, Value> = new Map()
+  for (const item of array) {
+    map.set(getKey(item), getValue(item))
+  }
+  return map
+}

src/mod.ts

@@ -11,6 +11,7 @@ export * from './array/intersects.ts'
 export * from './array/iterate.ts'
 export * from './array/last.ts'
 export * from './array/list.ts'
+export * from './array/mapify.ts'
 export * from './array/max.ts'
 export * from './array/merge.ts'
 export * from './array/min.ts'

tests/array/mapify.test.ts

@@ -0,0 +1,36 @@
+import * as _ from 'radashi'
+
+describe('mapify', () => {
+  const list = [
+    { id: 'a', word: 'hello' },
+    { id: 'b', word: 'bye' },
+    { id: 'c', word: 'oh' },
+    { id: 'd', word: 'hey' },
+    { id: 'e', word: 'ok' },
+  ]
+  test('returns correct map of values', () => {
+    const result = _.mapify(
+      list,
+      x => x.id,
+      x => x,
+    )
+    expect(result).toBeTypeOf(typeof new Map())
+    expect(result.size).toBe(5)
+    expect(result.get('a')?.word).toBe('hello')
+    expect(result.get('b')?.word).toBe('bye')
+  })
+  test('does not fail on empty input list', () => {
+    const result = _.mapify(
+      [],
+      (x: any) => x.id,
+      x => x,
+    )
+    expect(result).toBeTypeOf(typeof new Map())
+  })
+  test('defaults value to array item', () => {
+    const result = _.mapify(list.slice(0, 1), x => x.id)
+    expect(result).toBeTypeOf(typeof new Map())
+    expect(result.size).toBe(1)
+    expect(result.get('a')?.word).toBe('hello')
+  })
+})