Add fromArray()

Author: Vovan-VE

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## 1.0.1 (DEV)
+
+- Add: `fromArray()`;
+
 ## 1.0.0 (2022-06-27)
 
 - Initial release.

README.md

@@ -191,6 +191,29 @@ findKey(input, (_, k) => k === k.toUpperCase());
 
 See also `find()`.
 
+### `fromArray()`
+
+```ts
+fromArray(
+  array:   readonly T[],
+  calcKey: (item: T) => K,
+): ReadonlyMap<K, T>
+```
+
+Creates a map from simple array of items, calculating corresponding key for
+every item with the given callback `calcKey()`.
+
+```ts
+fromArray([1, 2, 3], (v) => v * 10)
+// => Map(3) { 10 => 1, 20 => 2, 30 => 3 }
+```
+
+This is a shortcut for commonly used operation:
+
+```js
+new Map(array.map(v => [calcKey(v), v]))
+```
+
 ### `getOr()`
 
 ```ts

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@cubux/readonly-map",
-  "version": "1.0.0",
+  "version": "1.0.1-dev",
   "description": "Functions to work with read-only maps",
   "keywords": [
     "map",

src/fromArray.ts

@@ -0,0 +1,26 @@
+/**
+ * Creates a map from simple array of items, calculating corresponding key for
+ * every item with the given callback `calcKey()`.
+ *
+ * ```ts
+ * fromArray([1, 2, 3], (v) => v * 10)
+ * // => Map(3) { 10 => 1, 20 => 2, 30 => 3 }
+ * ```
+ *
+ * This is a shortcut for commonly used operation:
+ *
+ * ```js
+ * new Map(array.map(v => [calcKey(v), v]))
+ * ```
+ *
+ * @param array
+ * @param calcKey
+ */
+function fromArray<T, K>(
+  array: readonly T[],
+  calcKey: (item: T) => K,
+): ReadonlyMap<K, T> {
+  return new Map(array.map(item => [calcKey(item), item]));
+}
+
+export default fromArray;

test/fromArray.test.ts

@@ -0,0 +1,22 @@
+import fromArray from '../src/fromArray';
+
+it('creates map', () => {
+  interface T {
+    id: number;
+    name: string;
+  }
+
+  const array: T[] = [
+    { id: 10, name: 'John Random' },
+    { id: 20, name: 'Pupkin Vasily' },
+    { id: 30, name: 'Lu Lu' },
+  ];
+
+  expect(fromArray(array, v => v.id)).toEqual(
+    new Map([
+      [10, { id: 10, name: 'John Random' }],
+      [20, { id: 20, name: 'Pupkin Vasily' }],
+      [30, { id: 30, name: 'Lu Lu' }],
+    ]),
+  );
+});