feat(maybe): add valueOrNull() (#161)

Author: patrickmichalina

package-lock.json

@@ -32,6 +32,11 @@ export interface IMaybe<T> extends IMonad<T> {
    */
   valueOrUndefined(): T | undefined
 
+  /**
+   * Unwrap a Maybe with its value or return null if its empty
+   */
+  valueOrNull(): T | null
+
   /**
    * Unwrap a Maybe with its value or return and empty list
    */

src/maybe/maybe.interface.ts

@@ -394,6 +394,22 @@ describe('Maybe', () => {
     })
   })
 
+  describe('when returning a value or null', () => {
+    it('should handle "none" case', () => {
+      const sut = undefined as string | undefined
+      const maybeAString = maybe(sut).valueOrNull()
+
+      expect(maybeAString).toBeNull()
+    })
+
+    it('should handle "some" case', () => {
+      const sut = 'actual input' as string | undefined
+      const maybeAString = maybe(sut).valueOrNull()
+
+      expect(maybeAString).toEqual('actual input')
+    })
+  })
+
   describe('when returning an array', () => {
     it('should handle "none" case', () => {
       const sut = undefined as string | undefined

src/maybe/maybe.spec.ts

@@ -32,6 +32,10 @@ export class Maybe<T> implements IMaybe<T>  {
     return this.isSome() ? this.value as NonNullable<T> : undefined
   }
 
+  public valueOrNull(): T | null {
+    return this.isSome() ? this.value as NonNullable<T> : null
+  }
+
   public valueOrCompute(fn: () => NonNullable<T>): NonNullable<T> {
     return this.isSome() ? this.value as NonNullable<T> : fn()
   }

src/maybe/maybe.ts

@@ -7,6 +7,10 @@
       "es2015",
       "dom"
     ],
+    "types": [
+      "node",
+      "jest"
+    ],
     "isolatedModules": false,
     "experimentalDecorators": true,
     "emitDecoratorMetadata": true,
@@ -27,6 +31,6 @@
     "downlevelIteration": true
   },
   "include": [
-    "src/**/*.ts"
+    "src"
   ]
 }