feat: Created ValueOf<T> util type (#1203)

resolves #1202

Author: bmingles

packages/utils/src/TypeUtils.test.ts

@@ -0,0 +1,12 @@
+import { ValueOf } from './TypeUtils';
+
+describe('ValueOf', () => {
+  it('should derive the value type', () => {
+    const x = { a: 1, b: 2, c: 3 } as const;
+
+    // eslint-disable-next-line @typescript-eslint/no-unused-vars
+    const y: ValueOf<typeof x>[] = [1, 2, 3];
+
+    // No assertion since this is a types only test
+  });
+});

packages/utils/src/TypeUtils.ts

@@ -0,0 +1,13 @@
+/**
+ * Util type to extract the value from an object.
+ *
+ * e.g. Given
+ * declare const x: { a: 1; b: 2; c: 3 };
+ *
+ * The value type can be extracted like this:
+ * type A = ValueOf<typeof x>; // 1 | 2 | 3
+ *
+ * Instead of the more verbose:
+ * type A = typeof x[keyof typeof x]; // 1 | 2 | 3
+ */
+export type ValueOf<T> = T[keyof T];