feat: Value

Signed-off-by: Lexus Drumgold <[email protected]>

README.md

@@ -35,6 +35,7 @@
     - [`fn(node[, index][, parent])`](#fnnode-index-parent)
   - [`Type<[T]>`](#typet)
   - [`Uint`](#uint)
+  - [`Value<[T]>`](#valuet)
 - [Contribute](#contribute)
 
 ## What is this?
@@ -74,7 +75,8 @@ import type {
   PositionalInfo,
   Test,
   TestFunction,
-  Type
+  Type,
+  Value
 } from '@flex-development/unist-util-types'
 ```
 
@@ -252,6 +254,15 @@ Range: `[0, 10]`
 
 > **source**: [`src/uint.ts`](src/uint.ts)
 
+### `Value<[T]>`
+
+Extract the `value` of [*tree*][tree] `T`.
+
+- `T` ([**`Node`**][node]): tree to extract value from
+  - **default**: [`Literal`][node]
+
+> **source**: [`src/value.ts`](src/value.ts)
+
 ## Contribute
 
 See [`CONTRIBUTING.md`](CONTRIBUTING.md).

src/__tests__/value.spec-d.ts

@@ -0,0 +1,17 @@
+/**
+ * @file Type Tests - Value
+ * @module unist-util-types/tests/unit-d/Value
+ */
+
+import type * as mdast from 'mdast'
+import type TestSubject from '../value'
+
+describe('unit-d:Value', () => {
+  it('should equal T["value"]', () => {
+    // Arrange
+    type T = mdast.Text
+
+    // Expect
+    expectTypeOf<TestSubject<T>>().toEqualTypeOf<T['value']>()
+  })
+})

src/index.ts

@@ -22,3 +22,4 @@ export type { default as Test } from './test'
 export type { default as TestFunction } from './test-function'
 export type { default as Type } from './type'
 export type { default as Uint } from './uint'
+export type { default as Value } from './value'

src/value.ts

@@ -0,0 +1,21 @@
+/**
+ * @file Value
+ * @module unist-util-types/Value
+ */
+
+import type { Literal, Node } from 'unist'
+
+/**
+ * Extract the value of from [*tree*][1] `T`.
+ *
+ * [1]: https://github.com/syntax-tree/unist#tree
+ *
+ * @see {@linkcode Literal}
+ * @see {@linkcode Node}
+ * @see https://github.com/syntax-tree/unist#literal
+ *
+ * @template {Node} [T=Literal] - Tree to try extracting value from
+ */
+type Value<T extends Node = Literal> = T extends Literal ? T['value'] : never
+
+export type { Value as default }