Add new type: ValuesType

README.md

@@ -106,6 +106,7 @@ Issues can be funded by anyone and the money will be transparently distributed t
 * [`Subtract<T, T1>`](#subtractt-t1)
 * [`Overwrite<T, U>`](#overwritet-u)
 * [`Assign<T, U>`](#assignt-u)
+* [`ValuesType<T>`](#valuestypet)
 
 ## Special operators
 
@@ -586,6 +587,34 @@ type ExtendedProps = Assign<Props, NewProps>;
 
 [⇧ back to top](#table-of-contents)
 
+### `ValuesType<T>`
+
+Get the union type of all the values in an object, tuple, array or array-like type `T`.
+
+**Usage:**
+
+```ts
+import { ValuesType } from 'utility-types';
+
+type Props = { name: string; age: number; visible: boolean };
+// Expect: string | number | boolean
+type PropsValues = $ValuesType<Props>;
+
+type NumberArray = number[];
+// Expect: number
+type NumberItems = $ValuesType<NumberArray>;
+
+type ReadonlyNumberTuple = readonly [1, 2];
+// Expect: 1 | 2
+type AnotherNumberUnion = $ValuesType<NumberTuple>;
+
+type BinaryArray = Uint8Array;
+// Expect: number
+type BinaryItems = $ValuesType<BinaryArray>;
+```
+
+[⇧ back to top](#table-of-contents)
+
 ### `Partial<T>`
 
 Make all properties of object type optional

src/__snapshots__/mapped-types.spec.ts.snap

@@ -182,4 +182,22 @@ exports[`SymmetricDifference testType<SymmetricDifference<'1' | '2' | '3', '2' |
 
 exports[`Unionize testType<Unionize<Props>>() 1`] = `"{ name: string; } | { age: number; } | { visible: boolean; }"`;
 
+exports[`ValuesType testType<ValuesType<[1, 2]>>() 1`] = `"1 | 2"`;
+
+exports[`ValuesType testType<ValuesType<Props>>() 1`] = `"string | number | boolean"`;
+
+exports[`ValuesType testType<ValuesType<ReadonlyArray<string>>>() 1`] = `"string"`;
+
+exports[`ValuesType testType<ValuesType<Uint8Array>>() 1`] = `"number"`;
+
+exports[`ValuesType testType<ValuesType<Uint16Array>>() 1`] = `"number"`;
+
+exports[`ValuesType testType<ValuesType<Uint32Array>>() 1`] = `"number"`;
+
+exports[`ValuesType testType<ValuesType<number[]>>() 1`] = `"number"`;
+
+exports[`ValuesType testType<ValuesType<readonly [1, 2]>>() 1`] = `"1 | 2"`;
+
+exports[`ValuesType testType<ValuesType<readonly symbol[]>>() 1`] = `"symbol"`;
+
 exports[`WritableKeys testType<WritableKeys<ReadWriteProps>>() 1`] = `"\\"b\\""`;

src/index.ts

@@ -48,6 +48,7 @@ export {
   Subtract,
   SymmetricDifference,
   Unionize,
+  ValuesType,
   WritableKeys,
 } from './mapped-types';
 

src/mapped-types.spec.snap.ts

@@ -39,6 +39,7 @@ import {
   PickByValueExact,
   OmitByValueExact,
   Optional,
+  ValuesType,
 } from './mapped-types';
 
 /**
@@ -501,3 +502,28 @@ type RequiredOptionalProps = {
   // @dts-jest:pass:snap -> Optional<Props, "age" | "visible">
   testType<Optional<Props, 'age' | 'visible'>>({ name: 'Yolo', age: 99 });
 }
+
+// @dts-jest:group ValuesType
+{
+  // @dts-jest:pass:snap -> string | number | boolean
+  testType<ValuesType<Props>>();
+
+  // @dts-jest:pass:snap -> number
+  testType<ValuesType<number[]>>();
+  // @dts-jest:pass:snap -> symbol
+  testType<ValuesType<readonly symbol[]>>();
+  // @dts-jest:pass:snap -> string
+  testType<ValuesType<ReadonlyArray<string>>>();
+
+  // @dts-jest:pass:snap -> 1 | 2
+  testType<ValuesType<[1, 2]>>();
+  // @dts-jest:pass:snap -> 1 | 2
+  testType<ValuesType<readonly [1, 2]>>();
+
+  // @dts-jest:pass:snap -> number
+  testType<ValuesType<Uint8Array>>();
+  // @dts-jest:pass:snap -> number
+  testType<ValuesType<Uint16Array>>();
+  // @dts-jest:pass:snap -> number
+  testType<ValuesType<Uint32Array>>();
+}

src/mapped-types.spec.ts

@@ -39,6 +39,7 @@ import {
   PickByValueExact,
   OmitByValueExact,
   Optional,
+  ValuesType,
 } from './mapped-types';
 
 /**
@@ -501,3 +502,28 @@ type RequiredOptionalProps = {
   // @dts-jest:pass:snap
   testType<Optional<Props, 'age' | 'visible'>>({ name: 'Yolo', age: 99 });
 }
+
+// @dts-jest:group ValuesType
+{
+  // @dts-jest:pass:snap
+  testType<ValuesType<Props>>();
+
+  // @dts-jest:pass:snap
+  testType<ValuesType<number[]>>();
+  // @dts-jest:pass:snap
+  testType<ValuesType<readonly symbol[]>>();
+  // @dts-jest:pass:snap
+  testType<ValuesType<ReadonlyArray<string>>>();
+
+  // @dts-jest:pass:snap
+  testType<ValuesType<[1, 2]>>();
+  // @dts-jest:pass:snap
+  testType<ValuesType<readonly [1, 2]>>();
+
+  // @dts-jest:pass:snap
+  testType<ValuesType<Uint8Array>>();
+  // @dts-jest:pass:snap
+  testType<ValuesType<Uint16Array>>();
+  // @dts-jest:pass:snap
+  testType<ValuesType<Uint32Array>>();
+}

src/mapped-types.ts

@@ -576,3 +576,41 @@ export type Optional<T extends object, K extends keyof T = keyof T> = Omit<
   K
 > &
   Partial<Pick<T, K>>;
+
+/**
+ * ValuesType
+ * @desc get the union type of all the values in an object, array or array-like type `T`
+ * @example
+ *    type Props = { name: string; age: number; visible: boolean };
+ *    // Expect: string | number | boolean
+ *    type PropsValues = ValuesType<Props>;
+ *
+ *    type NumberArray = number[];
+ *    // Expect: number
+ *    type NumberItems = ValuesType<NumberArray>;
+ *
+ *    type ReadonlySymbolArray = readonly symbol[];
+ *    // Expect: symbol
+ *    type SymbolItems = ValuesType<ReadonlySymbolArray>;
+ *
+ *    type NumberTuple = [1, 2];
+ *    // Expect: 1 | 2
+ *    type NumberUnion = ValuesType<NumberTuple>;
+ *
+ *    type ReadonlyNumberTuple = readonly [1, 2];
+ *    // Expect: 1 | 2
+ *    type AnotherNumberUnion = ValuesType<NumberTuple>;
+ *
+ *    type BinaryArray = Uint8Array;
+ *    // Expect: number
+ *    type BinaryItems = ValuesType<BinaryArray>;
+ */
+export type ValuesType<
+  T extends ReadonlyArray<any> | ArrayLike<any> | Record<any, any>
+> = T extends ReadonlyArray<any>
+  ? T[number]
+  : T extends ArrayLike<any>
+  ? T[number]
+  : T extends object
+  ? T[keyof T]
+  : never;