feat: mapValues

src/map-values.spec.ts

@@ -0,0 +1,27 @@
+import { mapValues } from './map-values';
+
+describe('mapValues', () => {
+  it('should apply the callback to every value of the source', () => {
+    const o = {
+      one: 1,
+      two: 2,
+      three: 3,
+      four: 4,
+    };
+    const e = {
+      one: 2,
+      two: 4,
+      three: 6,
+      four: 8,
+    };
+    const result = mapValues(o, item => item + item);
+    expect(result).toEqual(e);
+  });
+
+  it('should support strings', () => {
+    const o = { one: 'one' };
+    const e = { one: 'ONE' };
+    const result = mapValues(o, item => item.toUpperCase());
+    expect(result).toEqual(e);
+  });
+});

src/map-values.ts

@@ -0,0 +1,17 @@
+/**
+ * Creates an object with the same keys as the `source` object and values generated by running each own enumerable property of `source` thru the `fn` function.
+ *
+ * @param source Object to map the values from.
+ * @param fn Function to apply to each value.
+ */
+
+export function mapValues<T, K extends keyof T>(
+  source: T,
+  fn: (value: T[K], key: K) => T[K]
+) {
+  const entries = Object.entries(source).map<[K, T[K]]>(([key, value]) => [
+    key as K,
+    fn(value, key as K),
+  ]);
+  return Object.fromEntries(entries);
+}

tsconfig.json

@@ -17,7 +17,6 @@
     "paths": {
       "*": ["src/*", "node_modules/*"]
     },
-    "jsx": "react",
     "esModuleInterop": true
   }
 }