Merge pull request #92 from thomasperi/master

Fix reactive array splice bug when called with single argument

src/__tests__/reactive.spec.ts.ts → src/__tests__/reactive.spec.ts

@@ -301,4 +301,11 @@ describe('reactive', () => {
     await nextTick()
     expect(callback.mock.calls[2][0]).toBe(500)
   })
+
+  it('should preserve argument count for splice', () => {
+    const data = reactive([1, 2, 3, 4, 5])
+    const tail = data.splice(2)
+    expect(data).toEqual([1, 2])
+    expect(tail).toEqual([3, 4, 5])
+  })
 })

src/reactive.ts

@@ -325,8 +325,14 @@ function arrayOperation(
     case 'fill':
       return (...args: any[]) => synthetic(...args.map((arg) => r(arg)))
     case 'splice':
-      return (start: number, remove?: number, ...inserts: any[]) =>
-        synthetic(start, remove, ...inserts.map((arg) => r(arg)))
+      return function (start: number, remove?: number, ...inserts: any[]) {
+        // Preserve the argument count when there's only one argument,
+        // because if a second argument is passed but undefined,
+        // it gets treated as 0.
+        return arguments.length === 1 ?
+          synthetic(start) :
+          synthetic(start, remove, ...inserts.map((arg) => r(arg)))
+      }
     default:
       return native
   }